Maybe, but that has nothing to do with OAuth. One could be completely within the OAuth spec and allow one user to provide grants to act as dozens of other users

Maybe, but that has nothing to do with OAuth. One could be completely within the OAuth spec and allow one user to provide grants to act as dozens of other users. You are basically saying that OAuth is not good at something it was never designed to have any say about. It's as though you're saying that your rolling pin doesn't work well as a meat tenderizer. Yeah, I guess they're related, but that's not what a rolling pin does.