I would assume he's swapping the 111 front subframe with a 108 one with vented discs so he doesn't need to remove & swap hubs (and calipers, since the vented ones are probably bigger). If his donor has all good rubber bits & bushings it would probably be faster than doing just the hubs & replacing the other bits later on.

BTDT, only need to bleed the fronts on a dual-circuit setup if only the fronts have been drained.