There are legitimate reasons for this, e.g. imagine an employee at a company that uses Office365 needing to set up an account for Google Adwords.
So anyone with an example.com email can make a google account using that email as their login. Verify they have the email and that's their login. A common system for users who need to use google ads or analytics.
But when the company disables 365 login the google account remains. And if you use something third party that offers a "Sign in with google" then assumes because you have a google account ending "example.com" you are verified as "example.com" you've got access even if that account is disabled.
If you have the google admin portal this doesn't work as you're controlling it there. But signing up for Microsoft or Apple accounts with that google workspace address might have the same loophole.
If there's a way to do this, I would greatly appreciate a link or brief explanation, as our process for employee termination/resignation does involve disabling in the Google admin portal and if we need to be more proactive I definitely want to know.