The gunsmiths who have a problem are not taking their time to work with them right... Call the guys at Mile High they are doing Proof Barrels every week with no drama. You have to spend a couple of extra minutes indicating them right.
I have 3 Proof Barrels, all shoot sub 1/2 MOA and none wander... if you attempt to heat them up as hot as possible they will give you excessive mirage which will cause you problems but that is not the barrel wandering that excessive mirage in the scope. Big difference. I posted this stuff on my YT channel. In fact my RPR still has the Proof Barrel on it.
Bryan's results are a bit bogus as I believe Cal from PRB did the testing and did some funky, out of the normal stuff, which would not surprise me. Nobody I know agrees with those results and it has been mentioned several times that it is bs in the reporting. They don't always do things correctly.
I found the Hardy to not be as accurate as my Proof Barrels. The Hardy is good, it's on my Tikka Build, and I have shot a Hardy at my range tht was very accurate. (Not my rifle) but for my personal results the Proof Barrels are better. At 100 yards the Hardy is about a 5/8s to 1" shooter, on steel you can mask that pretty easy. My Proof Barrels are more accurate.