Privacy question: What is exposed to Apple by the iCloud account login requirement?

[paul]

Privacy question:
*What exactly is exposed to Apple by the iCloud account login requirement?*

As most adults know, Android works perfectly fine _without_ ever setting the
phone to any account, let alone a Google Account, which is a privacy boon.

Notice what I said which is that you can still _have_ a Google Account, and
you can still access your email, and your youtube subscriptions, and you can
still download apps from the Google Play repository, and you can still use
the Google search engines, and you can still use Google Maps, and you can
still update your OS, etc., *all without setting the phone to an account!*

By way of stark contrast, while _almost_ all that is also possible on iOS,
the _one_ horrid requirement of iOS is that you _must_ be logged into an
iCloud account if you ever want to install any apps from the App Store.

While you can set up iOS to not log into your iCloud account, if you do, you
lose all possibility of loading apps (we're always talking not
rooted/jailbroken here, as that's what the vast majority of people are).

Hence, the start truth is:
a. On Android, you don't even _have_ that privacy hole to plug.
b. On iOS, you do.

The question here isn't whether that privacy hole exists on iOS.
The fact is, it does exist on iOS.

The question here is simply that of the privacy implications of that fact.
*What exactly is exposed to Apple by the iCloud account login requirement?*
--
Note the apologists will likely claim "nothing"; but that's not an answer
as it's impossible that some personal data isn't transferred to Apple.