You must have used some weird other SSO systems is the only explanation I have.
GitHub has all the normal SSO stuff as anything else we use, but on top of the GitHub-specific account login. Everywhere else I just log in via SSO, in GitHub I log in first to GitHub (with its own MFA) and then the same SSO step as anywhere else.
I've never had to log in to Github as part of my daily flow. Only once to set up a new computer. Are you logging in using an incognito window or something?
Interesting. Perhaps it's because I'm not using GitHub daily, we're migrating to GitHub so I still do work in repos which live in the old system. Also, perhaps I'm more affected because I'm doing org admin stuff as well.
GitHub has all the normal SSO stuff as anything else we use, but on top of the GitHub-specific account login. Everywhere else I just log in via SSO, in GitHub I log in first to GitHub (with its own MFA) and then the same SSO step as anywhere else.