Ah, so to balance this you effectively delay the fighter's action surge feature to L10 level 2, instead of giving it at level 1 like you would if L1 was just a combination of the traditional levels 1 and 2. This way, it really is one level worth vs one level worth. And then the next subclass feature is balanced against L10 lvl 2, which is effectively like taking fighter to the traditional 4th level, but since Fighter 3 and 4 are just subclass feature and ASI, you're really only getting another one level worth of stuff (action surge). Does it work that way throughout?
In the case of multiclassing into a caster, your spell progression really does go two traditional levels at a time, but on the flip side you miss out on subclass features. Whereas if you multiclass out of a caster, you still keep your full spell progression, only giving up subclass features in exchange for the next level in your secondary class. So maybe that's ok?