I don't know who is telling you 6.2gr to 6.4gr is an alright charge especially when Accurate is listing a Max charge of 5.4gr AA#5 under a 124gr lead bullet. A charge of 6.4gr is a full grain higher which works out to 18.5% over the Accurate Max charge. In such a small case like the 9mm that is probably a very dangerous situation especially since Accurate's 5.4gr charge is reported @34,557 PSI. (just below the Max pressure for the cartridge)
I highly recommend you do not listen to what "people" are telling you when the powder company is telling you something so different. BTW, who are these people you speak of?
Again, adding an additional 18.5% to a load that's already bumping up against the SAAMI pressure limits in a small case like the 9mm is just asking for serious trouble. (who are these people?)