i am not certain about this and it definitely wouldn't apply to many plugins such as some of the Waves plugs, but isn't the fact that Logic uses 32 bit floating point processing, make internal clipping non uniform. ie Not all signal paths work the same way.
TDM is 48bit fixed AFAIK, making this sort of feature more pertinent.
As I mentioned, i am not totally sure about this, as I do have plugs that clip and the behaviour of most is dependent on level.