No, I think he ran into the same problem as I did. When you register with a SSO, Flarum doesn't give you the chance to set a password to make auth changes. I believe it's related to flarum/core674, which was "fixed" by removing the SUDO mode (that required a password for these changes).
It's possible there was a regression or it wasn't fixed properly for Twitter. Or that I'm off base here.