Also, seems like you’re probably a developer? If so, SSO, OAuth2, OIDC, etc. are worth learning about. You seem to be confusing/conflating SSO and OAuth2 authorization code flows, when they’re reasonably different things.

That said GitHub should have banned that website for lying and abusing instead of OP.

It makes a possibly dodgy website look more secure and legit by using a well known provider like Github for the login process.

In addition, it potentially exposes data from that well known provider, which is often sensitive data, as in the case of Github.

Or maybe I shouldn't just take everything at face value and pay attention to what I'm doing.

What is strange is that you are banned for an action someone else took. That doesn’t make any sense.