Same happens to me. I have the original creation email, my email is (was?) the backup email originally created. I know the date and time of creation of the account, and they still reject it.
That's what adding a recovery email is for: to deliberately weaken your account's security, in exchange for convenience.
If you disable recovery, then -- no surprise -- you won't be able to access your account if you lose access.
This post may seem unkind, but keep in mind that some people deliberately do not add recovery methods, in order to prevent secondary-takeover access; and that the above poster's request would fundamentally drastically weaken the security of those users.