It's a red herring. In addition to the IDFA, Apple has something called the IDFV (identifierForVendor). This ID is unique to a publisher, i.e. if a user has 3 of your apps installed, all three will share the same IDFV, so you can even do cross-app or cross-selling analytics. What you cannot do by design is use IDFV to build a cross-publisher dossier on users, or target users based on that ID other than on your own apps.
Apple hasn't put any restrictions on IDFV, only on IDFA, which was designed, well, for advertising and needs to be reined-in due to abuses in the Wild West everything goes world of the AdTech surveillance-industrial complex. In fact the existing opt-out "Limit Ad Tracking" setting that already implements what will become opt-in with iOS 14.5 does not apply to IDFVs.
Back in 2010 Steve Jobs himself had banned analytics altogether when Flurry's VP of Marketing blabbed and disclosed the existence of the then secret iPad: