That gunsmith list is extensive, but by no means complete, it relies on gunsmiths going and registering their business on it.
Yes, hand tightening a barrel is not the proper way to check headspace, but in this case it pointed out the error of the man's method. The headspace would get tighter as you tighten the barrel up further.
Never try to educate someone who resists knowledge at all costs.
But what do I know?