Consent should be opt-in and granular (a user might wish to opt-in for one app but opt-out for another one) so every app should’ve already implemented their own toggle (like iOS 14 would force them to) instead of just using it in the background and pointing users to the system-wide setting if they want to opt-out (which isn’t ideal if the user wants to remain opted-in for some apps only).
First of all under GDPR, tracking can be for a legitimate interest, and thus it might not require opt-in. For example security, or even first-party analytics, with the purpose of optimizing the content, can be legitimate interests. However this cookie is meant for advertising, and user profiling for marketing purposes doesn't pass the test for legitimate interest.
The other problem, for Apple, might be the revised E-Privacy Directive. You can't set such tracking cookies without informing users. Such cookies must be opt-in, whether you use them or not.
AFAIK Apple is simply complying with the law, whereas Facebook is effectively arguing for unlawful tracking, because that's just who they are.
Given that this feature is entirely made by Apple, that's not a reasonable conclusion.