To help keep things anonymous and to regain control.
For example: I could go to GMail and click "Generate new disposable alias" or whatever.
It would give me something like mUa8cDjyBJyCi@gmail.com which I could use anywhere.
All emails would still go to my main email. I have the option to reply to any emails from my alias or from my real email.
If a disposable alias gets compromised I can delete it. It would be hard to keep track so I assume there would be a search feature where I could type my alias in, and then click delete. Still keep my old email.
This is better than current aliases as email+alias@gmail.com still exposes your real email, which you can never delete, only create new, meaning people can spam you forever.
>For email uses, a textual encoding of a hashcash stamp is added to the header of an email to prove the sender has expended a modest amount of CPU time calculating the stamp prior to sending the email. In other words, as the sender has taken a certain amount of time to generate the stamp and send the email, it is unlikely that they are a spammer. [1]
You could then take it a step further by ONLY allowing emails to your aliases. Not to your main. So you can basically eliminate spam mail completely.
Except for the fact that it ties you to Apple, not Google (in your description, Google could still link all your aliases together), what you describe is very similar to https://en.wikipedia.org/wiki/Sign_in_with_Apple.
If you want to prevent that, a way to do that is by having a personal domain, and have all mail sent to whatever email addresses at that domain you want this to happen for forwarded to your personal domain.