This is similar to:
except that when a user is staged, meaning that it came in via
email in, and after their account is activated (either by the admin or by sending out an activation email which they reacted to), they can log into the system and do things like a regular user.
Except that they user account stays staged. There is no way to clear the staged flag.
So, user needs to be automatically unstaged not only when loggin in via OAuth, but simply when they are activated via any means.