I think those are legit. Guessing you need a gmail or gsuite address to publish?
Perhaps it's like YouTube? You cannot buy or use a Youtube Premium subscription with a Google Workspace account. I tried inviting a family member to my Youtube Premium subscription, using her Google Workspace email. It doesn't work, because Youtube doesn't see it as a Gmail account.
All you'd need to actually work would be email, so some MX records on a subdomain. Is it ideal? No. Is it better than all of your users having no way to verify that a Chrome extension is actually you? Infinitely better.
vs. months of emails and meetings for something that more or less achieves the same result
ever wondered why these large companies end up running things on random domains?
this is why