slotted and or drilled rotors

Holes are evil, rotors crack at the holes. Anything will crack at a hole, but the thermal growth of a rotor puts huge internal stresses in it and the holes are major stress risers.

An engineer designed those rotors, sure, but two things happened after that. Marketing said that the market wants holes in the rotors and made enough of a case for it with accounting that the engineers were over-ruled. BT, DT.