I wonder if the exrtra res is bringing out the grain - like good speakers making a bad recording sound worse.
It is indeed the resolution of the Blu-ray disc exceeding the master which allows one to see the grain. But I don't think of it as a bad thing, it is just proof that you are seeing every bit of detail that was originally recorded.
Perhaps it is because I'm a photographer and I've long since become used to seeing film grain that is doesn't bother me as much as it seems to other people. I say embrace the grain, it is an organic part of the picture.
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs