You should read the actual proposal. I think you have a few facts wrong.
1. Data sharing on app store downloads is now opt in.
2. Apple apps are exempt because they are managed by different settings. You cannot opt out.
3. FB and Apple both plan to use this data to target their ad networks.
1. It is not data share, it is advertising identifier (idfa) you will still have access to (idfv) vendor identifier.
2. Apple apps are not exempt. (Even weather app is asking for location permission after permission change about location, this is no different)
3. Yeah apple and google are after data from other applications, applications you installed, how much you are using, basically everything. Amount of idfa provides is unbelievable.
So still facebook can track you in facebook apps.