[zefei]

The default _browser_ will mostly be Safari. But the moment webkit requirement is relaxed, all in-app browsers for Facebook, TikTok, Youtube, Instagram, etc will be replaced with their own forks without any respect for "do not track". They will become the second most used browsers on iPhone, not Firefox or Chrome.

[smoldesu]

Seeing how this didn't really happen on Android, Windows, Linux or MacOS, I don't think there's any evidence to support this theory.