It is likely this is a heuristic; Apple would lose out disallowing major companies, so rules are sometimes shifted, if not explicitly for all. Snapchat being pulled would cause a minor exodus, I imagine, especially if it was heavily leaned on that Apple were responsible for their removal.

That is likely true, but slipping in a call to list_lio would be really easy to do. Even if they had a check for the syscall instruction in this case, you could just ROP your way to libc…

It would probably kill snapchat and force many groups to other platforms.

It’s possible for both to happen. People might switch chat apps in the short term, but reconsider buying an iPhone in the next cycle (esp. if Apple makes a habit of killing off popular apps).