Even if your google account is deleted, the email address is NOT recycled because it can be used to impersonate people - maybe the previous owner still has physical/digital accounts linked to that old email. As far as I know most services do this - an email address once registered is never released again.

Unused they have a half-life. Google Voice numbers much more aggressively so.

It's somewhere in the document.

This answer is not actually correct. I have an account I deleted 18 years ago, still can’t make it again.

Could in theory be because someone else grabbed the account 16 years ago tho, unless I'm missing something?

No Google does not allow creating a new account with a previously-used Gmail address. Each Gmail address can be used at most once.

I emailed the address to make sure: It bounce due to not existing.

You can never make another account with that address because Google does not delete things.