Per usual, your insights are immaculate. I would ad my opinion that Switter listings will be BP v2 (which, actually, was Craigslist V2).

I also think that the almost immediate response to SESTA was because everyone was basically already rewriting their TOU/TOS in response to the new EU privacy laws going into effect. Not saying that their moves wouldn't have happened, just that many sites had new policies even before the law was passed because they already had groups working on the rewrites.