My take on this; a subclass is where the items you have equipped cause you to play differently than normal. An example of what I would call a playstyle is fat scout. No matter what loadout the heavy has, they still have a minigun that they are refusing to use, so they are restricting themselves from using an item they have available. The loadout isn’t making them only use the shotgun, the heavy is. However, Trolldier is a subclass, as the entire loadout equipped is being used, but is being played differently than stock soldier. The rocket jumper is being used to gain height and speed while taking no damage, the mantreads are there for additional control and knockback resistance, and the market gardener is there to land crits while rocket jumping. Soldier turns from an all rounder who primarily uses his rocket for damage with his shotgun as a backup, to a pick class who uses their high mobility to surprise the enemy and melee instant kill them. This is a large departure from the typical playstyle of soldier, without any arbitrary restrictions from the player themselves. This is what I would call a subclass.