He also has a Google Account with the Google Account ID of email@example.com. I think he created it somehow with YouTube. (He has a cognitive disability which doesn't stop him from doing some weird shit I can't figure out.)
His second Google Account does not have the email address of firstname.lastname@example.org because that belongs to the Google Workspace account. Instead of it has an email of the form: email@example.com. If I send email to that gtempaccount.com address it redirects to firstname.lastname@example.org.
This feels like a security risk waiting to be exploited. It certainly is weird. It reminds me that Google Workspace accounts don't have the same meaning and privileges as full Google @gmail.com accounts.