This was a secondary AWS account in use by the company that had been in place for quite some time and that secondary account was just no longer needed. So to consolidate things down, it was deleted. Also at that time, SSO wasn't being used for anything with the company - and they were on a completely different email provider.

I'm not arguing that it was impossible to know the long term outcome here, but it doesn't mean it isn't frustrating. If you've spent any length of time working in AWS, you know that documentation can be difficult to find and parse.

I can certainly understand why the policy exists. What I think should be possible is in these situations to provide proof of ownership of the old email address so it can be released and reused somehow.