To tell you the truth 2F, I haven't really found that to be true either. I recently had a roll of APX400, shot at EI200, then mistakenly re-exposed at EI1600, and dev'd the whole thing for EI1600 times in D-76 1+0 and ended up with something like this:

Sure the whole thing was entirely unplanned and the APX had the highlights pounded, but I don't consider it grainy at all. Fairly normal (except for the tonality going off the map, of course).