Apple has less to fear from antitrust than Google in general, and particularly from taking hostile actions towards Facebook.
On the other hand, Facebook is not really a competitor to Apple, while Google very much is, so Apple has an incentive not to carry out an action that would strengthen Google.
https://www.theverge.com/2019/1/31/18206020/apple-facebook-i...
If the violations were serious enough, I think Apple/Google would consider some kind of temporary shutdown for the Facebook app if they thought they could weather the PR storm.