IANAL. Not sure about that. IDFA is essentially a tracking cookie.
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.
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.