Apple ID email addresses using custom domain

Hi,

Based on this chronology of events:

1. One uses {prefix}@{custom domain name} as Apple ID. The domain name is hosted externally.
2. One deletes the Apple account {prefix}@{custom domain name}. At the deletion point, the Apple amount still had the email address set as: {prefix}@{custom domain name}.
3. One creates a secondary Apple account on a secondary, non-relevant email address.
4. One adds a domain to the account as they use iCloud+. The nearly added domain name is {custom domain name}.
5. One attempts to create the email address: {prefix}@{custom domain name}.

When they follow step 5, they receive this error:

This email is already in use with another Apple ID.

Can Apple implement this as a new functionality?

• Consider the number of cases where genuine email addresses set on custom domains with prefixes such as admin@, administrator@, support@ and others are likely to be reused if brought into the Apple ecosystem through the private domain name route.
• If this is not a feature Apple is looking to invest in, then at least warn users when they create new Apple accounts that they will never be able to use that email address in any other instance in conjunction with Apple SMTP services.

Thoughts.