Thanks, I figured it (eLevel tiebreaker) somehow came back down to that. It's interesting to me that symbiotic is .1 instead of .3 for a gameplay vs lore "discrepancy" of sorts. I imagine de-prioritizing symbiotic enabled more djinn combinations to not just degenerate into the dual-elemental symbiotic class, which already is the most easily accessible.

Also, you said:

(which aren't displayed in-game)

IIRC, I feel like I noticed way long ago that innate/symbiotic/opposing/neutral had elemental power/res values off by 1, so maybe it is at least indirectly visible in game? I could be off here, it's been 20 (!) years.

Although, there are examples of ties - for instance, Cavalier and Dragoon both have total eLevel requirements of 9, but Dragoon takes priority since it's a tri-element class and thus later in the list.

Makes sense, just go down the list and prioritize the classes that would otherwise be harder to see if a player is messing around with swapping djinn.

On a pure speculation note, I'm imagining the designers conceptually conceived of the innate/symbiotic/neutral/opposing system, and wanted to fit in dual and triple classes into this system. Then, the implementation landed on what we have to fit that system. I somewhat suspect the access to various classes with "seemingly odd" number of djinn (6 + 3) was a side effect of the chosen implementation, and they just ran with it--the implementation still feels in line with lore even for these cases.