I think you are right. These players must be participting in some 3rd party affiliate rakeraces and leaderboards. Most of them have zero history on any other modes. Accounts created purely for playing AoF, so proly alternate accounts created under affiliate.In the GTO model I didn't use hands like T2. In EV model there may well be a situation when SB raise on BB with T2 can be profitable with low all-in percentage of BB player.
About the regulars, I've already written about them. It seems to me that they have some additional income from GG.
f you haven't read the full post, google "Why you shouldn't play All-in or Fold (AoF) on the GG network" (along with the quotes). In it I explain why AoF is not profitable.