That's the sites itself enabling that, most likely their auth provider has SSO with groogle https://developers.google.com/identity/gsi/web/guides/offerings htt

That's the sites itself enabling that, most likely their auth provider has SSO with groogle https://developers.google.com/identity/gsi/web/guides/offerings https://developers.google.com/identity/gsi/web/guides/offeri... Also, you can kinda-disable this per browser https://myaccount.google.com/security https://myaccount.google.com/security -> "Signing in to other sites"