"Apple gives you the ability to permanently delete your Apple ID account at any time and for any reason."

That said, it's a pretty massive wipe.

Photos, videos, documents, and other content that you stored in iCloud are permanently deleted; you can't receive any messages or calls sent to your account via iMessage, FaceTime, or iCloud Mail; and you can't sign in to or use services such as iCloud, the App Store, iTunes Store, Apple Books, Apple Pay, iMessage, FaceTime, and Find My iPhone. In addition, any Apple Store appointments and AppleCare support cases are canceled.

Deleting your Apple ID is permanent. After your account is deleted, Apple can't reopen or reactivate your account or restore your data.

You lose all your credits with apple (if any) app updates will stop working even for apps already downloaded and more.

"Manage Your Data and Privacy." On the following page, select "Get started" under "Delete your account."

The point is they enforce that third parties have to allow it from within the app itself rather than a website. But Apple's account deletion process is only available on their website.

Apple also says apps aren't allowed to use notifications for advertising (3.1.7 Advertising) but routinely uses notifications to advertise Apple Music, Apple TV, and their other various Apple+ services ¯\_(ツ)_/¯

That's an interesting corner case. Even if turnabout is fair play I wonder if it's even a good idea. If you have two devices, and you delete your Apple ID from one of them, do you brick the second device? I think there are dragons there.