It is possible to make a non-gmail and non-gsuite google account... Just it isn't obvious how to do so.

You need to go to any google signin page, click "Create account" > "For myself" > "Use my current email instead".

You can then use that to make chrome extensions.

> it is a corporate account that is managed by google

All the counter-examples I could find in the linked thread are Google Mail (for Business), which is functionally the same as requiring a gmail account in that it requires Google to be your mail-provider.

You can also create a Google Account using a non-Google e-mail address, without any special Google Business thing. I did. I keep a Google account tied to my work e-mail address, but there is no Gmail account associated with this Google account. I can use Google services, but all my mail is on our corporate servers.

A lot of people in corporations set things up without necessarily understanding what they're setting up. This includes apps. If you're thinking, "Wouldn't Microsoft know how to set things up correctly?" the answer is "Not necessarily". It's not "Microsoft" setting up some app account, it's a random guy on a random team somewhere in Microsoft, who might not have ever published an app before, much less gotten any training or done much investigation into it.

Thanks for the correction.