In 2 and (I think) 3, there was a fifth class of legs called "hover" that basically acted like quads do in hover mode in AC6, but bound to the ground unless you boosted. IIRC, they had the easiest time getting airborne from a boost, but had no unboosted jump. Basically, they were faster treads that could move sideways.

They've been gone since at least 4, though.