SBRs and AOWs have been well described, documented and legal for a looooooooooooong time. They could successfully represent in court case that AR pistol braces were allowed by them but folks started using them in a manner not approved by them (as stocks) and they would not exactly be lying. Not so with SBRs. That would require a change in the law as far as I understand it.
I’ve also heard many folks say that SBRs can’t be transported inside the car with you as handguns can. Agreed, but If it ever gets to the point that I feel I need my SBR on my lap while I drive I think I’ll be caring very little about what’s “legal” at that point because we’ll be talking complete collapse of civilization, at least locally.