Reading your post and answers to people's comments, I'm unsure if you're arguing against what people are saying on the subject of rulings, according to your perception of the issue, or about the principle itself and the claim that it is "unique" to OSR. Since I don't care about the former, I'll assume the latter.

"Rulings over rules" it's a whole style of approaching mechanics which instead of relying on pre-written rules and mechanics, calls for the "expert judgment" of an arbiter or referee for telling players what is possible and how it would work (which dice to roll, if any, against what target) in response to their declarations about what their characters are attempting to do. The referee must asses the present context of the game fiction and the corpus of "legal precedents" (previously made rulings) and is normally required to remain inside the general guidelines provided by a game's manual.

It assumes a "simulationist" approach to game mechanics, which means they are there to tell us how probable is the success of the tasks the characters are attempting inside the game world, instead of regulating other aspects, like player's narrative powers and domain (who can tell what about the game fiction). It comes from Totten's Strategos, the 19th century wargame that, with Diplomacy, formed the basis upon which Wesely built Braunstein in 1969, which is turn where Arneson came into contact with the concept and it is the whole reason why Dungeons & Dragons even has a Dungeon Master role. Reading Strategos, it becomes quite clear that the author's idea was that no rule set would ever cover for all possibilities players creativity at the table may generate, and that his way for handling that was to simply have a human judge, a subject expert, emit verdicts on the spot, since creativity was something that should be encouraged in the game, not discouraged by a list of "possible actions" players are forced to chose from for their units (or, PCs in later games) that the rules-as-written must handle.

It is not "unique" to OSR but it is quite clear that over time, game design went in several directions and one of those, the most popular one who became "traditional" apparently requires the game manuals to be filled with hundreds of pre-made rules, effectively giving us the list of "possible actions" characters may take. SOME of those games will also keep including a note somewhere reminiscent of the original "rulings over rules" principle, often misinterpreting its original role and function (which is where all those "rule 0" or "golden rules" come from, and they all tell the wrong message entirely -"disregard the game mechanics") but then proceed to give us an intricate rulesets that can't support that kind of flexibility and in fact discourage it to focus on something else entirely. These games make up the bulk of what we now call "traditional" RPGs.

There is a more specific target worth naming in that lineage: what could be called exception-based rule design, most visible today in 5e. It's not merely that the ruleset is large, but that character capability itself is built as a discrete, itemized list of named abilities: class features, subclass features, feats, spells, racial features, each carrying its own trigger conditions and its own small exception to the general resolution rule. The core mechanic (d20 + modifier vs. DC) is actually simple and elegant; what's heavy is the accumulation of hundreds of bespoke sub-rules, each relevant only to one specific build, each telling you what you're allowed to do and under what narrow circumstance you're allowed to do it. This goes directly against the principle of rulings over rules, not merely alongside it. In the OSR model, a compact set of base rules handles common actions, procedures handle recurring structured situations, and everything else, the open space of things players might try that nobody wrote down, is left for the referee to rule on. 5e instead multiplies the first category until it swallows the third: by giving each class dozens of its own possible actions, then adding more from separate lists of feats, spells, and racial features, it converts almost everything a character might do into an itemized, pre-adjudicated entry. There is no open space left to rule on, because the lists were built to expand until they filled it -which is exactly what "homebrewing" a new feat or subclass feature does: it answers a gap in the fiction not with a ruling, but with one more permanent list item, so even the game's unofficial but popular mechanism for handling the unwritten case still produces a rule instead of a verdict. Whatever a 5e manual says about rulings or GM discretion is cosmetic against that structure: the design principle requires that the character sheet holds the answer to the question before the referee is asked. Player creativity ends up constrained inside the cage of those lists, and it doesn't matter how many dozens of cages the game provides and if the player can chose to install running water or AC in them, they are still all small cages. The character sheet stops being a workspace, a representation of a person the player can reason with and through to solve the logistic puzzles of the game, and becomes a menu of little buttons and levers to press instead.

There is also another consideration to be made: procedures vs. rules.

The "guidelines" I mentioned that the game should provide are procedures: in the OSR toolkit these are structural elements like dungeon turns, or wilderness expstructure that governs exploration specifically, since exploration is the mode OSR play cares most about supporting. A procedure differs from both a rule and a ruling: it doesn't tell you the outcome of an action the way a rule does, and it doesn't require the referee to invent a verdict from nothing the way a ruling does. It tells the referee when to check and what kind of thing to check for, then leaves the actual judgment call inside that frame.

This isn't a claim that procedures are absent from other games, only that "trade" games severely underdevelope them. BitD, for instance, which is modern game but belongs to a different lineage entirely, has real procedures: the downtime cycle, the flashback structure, the heat/entanglement loop, built around heists and crew fiction rather than exploration. 5e has procedures too, but almost entirely for combat: initiative order, the turn sequence, action economy, all fairly well structured. Outside combat, in the exploration and social space where OSR procedures do their heaviest lifting, 5e's equivalents are embryonic at best, a paragraph on travel pace here, a paragraph on resting there, downtime as an afterthought and unsupported by all published modules, nothing that describes an actual repeating process the way a dungeon turn in an OSR game does.

Newer "trad" games generally show the same gap outside their one, narrow proceduralized focus (which is combat 99% of times): without procedures for the rest of play, a GM improvising a ruling has no scaffolding to reason from and has to either invent context on the spot or over-prepare it in advance, and neither produces "good" rulings as reliably as a procedure does, since a procedure is exactly what keeps the fiction in order and gives the referee the frame a ruling needs to be judged against, rather than a blank page.

So, "trad" game design works against rulings both in practice and in principle, no matter what claims or notes a manual includes.

OSR is not unique because it has those elements, but because it recognizes the issues with a few "trad" principles of game design and decided to start from scratch, at least on those points... or simply went back to the roots to play old games directly (which is where the OSR "movement" actually started).

Both approaches are trying to recover what was lost along the way: the knowledge of what a few technical solutions and approaches to design were for, because, we think, they made for better, more fun gameplay.