"Save in 1Password?" false positives for GitHub or Google logins

That's happened on various web sites and SSO platforms, but FastMail and GitHub is the most recent example.

What happened was, I received a GitHub notification email, I clicked the link on FastMail's web site to view the discussion in a new tab on GitHub, then I closed the GitHub tab and came back to FastMail's already open tab. Then the extension incorrectly assumed that I had used GitHub to login to FastMail and asked me to save it:

FastMail doesn't even support GitHub logins, but more importantly, I didn't navigate to a GitHub authentication link. I was already authenticated, I didn't login to GitHub. 

I can't reproduce this consistently, but it's annoying when it happens. It might even lead users to having incorrect login items saved if they don't notice what it is. That might cause frustration in future sign-in flows.