> advertisers data on which users have downloaded their app after seeing specific adverts.

No it doesn’t.

It provides aggregate statistics on downloads, just like any analytics server.

No data on users is shared.

This is honestly pretty reasonable. Apple already knows which apps I download and this is made fairly clear (you're logged into the App Store and your account lists all apps you obtained).

Apple also knows which App Store ads I saw given that their server sent them to me in the first place. The ads are (at least for now) limited to the App Store and don't carry over across the web or other Apple apps.

Thus I don't see the problem with Apple using the data they've already got to provide anonymized conversion metrics to app developers.

Please provide links or citations showing what information about a user is shared with advertiser.