Apple is very much a 'private from everyone but apple' company, they smartly just don't talk about it out loud. For their high level apps like TV and such, have things like privacy review. But their security, activation and map parts do record a lot of info.
Apple kindly publishes IP exception lists so you can still receive notifications, while blocking the rest of 17/8.
Since notifications are user-visible, one can audit for unexpected, non-notification traffic to Apple's advertised notification-only IPs.
If a large corporation officially advertises to enterprise customers a bounded, testable claim (e.g. traffic to these IP addresses is limited to notifications), then that claim can be subject to ongoing audit by the IT teams of multiple, independent, enterprises.
Verified accountability is far superior to trust. Step 1: vendor corporation makes a bounded, testable, claim.
They aren’t a monopoly as long as you don’t consider income demographics.