First of all, the changes affected those users who advertise their products (especially mobile apps) and are engaged in optimization, targeting, and web conversion using the internal tools of the social network. The ban on collecting customer data unless they have given permission to do so has severely limited the ability to personalize advertising and its performance. In response, Facebook began using Aggregated Event Measurement to minimize the impact of Apple's update.
According to experts, the fact that the company issued such a report confirms its previous concerns. It aims at warning investors about the impending deterioration of the situation. In terms of using App Tracking Transparency, for advertisers, it's not clear how to handle targeting changes since many users, in most cases, prefer not to allow applications to track their actions.