” But wether pistols, with a stock added, were short barreled rifles was not clear for quite a while...”
It was always clear that an actual stock was an NFA item.
The lack of clarity came in 2014 when the ATF appeared to give a thumbs up to a brace that had enough stock like characteristics that people were able to hold it to their shoulder like a stock.
Basically: stocks were always SBRs, braces on pistols were OK, but the grey area was created over the last ~8 years when braces were invented that were stock-like. ATF first said OK, then reversed themselves when they got very popular.
Regardless, I’ll stick to my main point - NFA is the problem, the brace issue is just a symptom.
Always is a long time. It did not become "clear" until well after WWII.
Regardless, I’ll stick to my main point - NFA is the problem, the brace issue is just a symptom. You main point is absolutely correct.