That was not what was told to me by hodgden last year, but who knows, maybe the booth vendors don't know anything either.
I have been loading 25.2, which is about 2700 Fps from a 16.5 inch barrel (ar), and stopped my load development when I was getting 3/4 inch groups at 75 yards with a red dot. Could it get better with higher charges? sure, but you'll be 90 rounds in and you'll be able to light a match from your hand guard. I like to keep my charges as low as possible in order to get a proper cycle, good accuracy, and be able to get 4-5 mags in before I let it cool down, but to each their own.