Presumably though, they just made the pistons smaller for road use?
Yes - this is how they've made them compatible with the existing shimano leavers. If the surface area was larger you'd get weird(er) lever throw and modulation issues assuming the distance the pads have to travel to hit the rotor is the same.
Also - the size of the pad is what is dictating the bite, not the amount of pots, although the later kinda defines the former. Again assuming everything else is equal.
Yeah, I don't really see the issue of 1, 2, 4 pots. If they've designed them taking into account the master cylinder size in the lever then all should be good.
Yes - this is how they've made them compatible with the existing shimano leavers. If the surface area was larger you'd get weird(er) lever throw and modulation issues assuming the distance the pads have to travel to hit the rotor is the same.
Also - the size of the pad is what is dictating the bite, not the amount of pots, although the later kinda defines the former. Again assuming everything else is equal.