Can someone explain in more granularity why this change would be damaging for Facebook? Naively, I would assume that after someone logs into the Facebook app,

Can someone explain in more granularity why this change would be damaging for Facebook? Naively, I would assume that after someone logs into the Facebook app, Facebook knows who they are, and thus there would be not much additional benefit to more tracking information. Is this about being able to track in third-party apps that use the Facebook SDK or run Facebook ads?