You're right about that. There isn't a lot of independent test data, and even less data from independent sources with the proper Mil-Spec'ed meter.
Hansohn Brothers did this properly done independent test with their BK2209. It shows ours as well, but the Q is the only one for sale currently. I'm guessing the first round was lower than the rest due to ammo inconsistency, no one was sure what caused it.
https://www.youtube.com/watch?v=2SvFGap-fXk