I found that test quite interesting as well, and that's why I've standardized on 5/8-24 thread (when possible) and 30-caliber brakes for everything 30-caliber and down. Even my 204 and 223 barrels run that thread pattern/brake.
Caveat- nearly every brake I have is also a suppressor mount, either TBAC CB or SiCo ASR.
i always use a break that is 1 size larger than i need (i.e. use a 6.5mm on a 6mm, or a 30cal on a 7mm) as i am paranoid about carbon build up in the break slowly closing diameter of the exit hole.