Never heard of that. The differences is obvious in diameter alone! 996, except for 4S, TT and GT models, and 997 Carrera have the same brake hardware, just as 987 Boxster S and Cayman S. The 997 Carrera S system is derived from the 996 TT system, just as the 997 Carrera S PCCB system is the same as on the 996 Turbo S.

Are you sure you didn't mix something up along the way?