Pistol Braced Firearm same as SBR? Or its own new NFA Category?

[Bret]

Every AR I own was built on a lower transferred as "other". That is the only thing either I or the ATF could prove or disprove.

Yep. I was mainly thinking about people buying pistols after the date of publication. That would be easy for the ATF to prove if they chose to dive in that far. Do be prepared to send a picture of the whole gun if they request it.