Mate defiantly the bore size difference is considerable , But between the 2 pots and brembos as a whole are physically the same size including the gap for the pad area . So the difference you see in size here is relative.

Hense why Doug and alot of others dont run rear Brembos . They even weigh around the same . Fronts obviously no comparison but rears are close to same size and shape just piston diameters differ . Your welcome to come past and compare in the flesh . The measurements are piston size the exposed part of the piston is tapered as you say and still big differences.