The case against MS was abusive licensing practices. MS blocked OEMs from choosing their own default browser, and charged OEMs a license fee even if the computers weren't running Windows. That doesn't apply to Apple which does not license their OS.

Android and ChromeOS both technically allow other browser engines, but in practice non-Chromium browsers are a rounding error on those platforms. You can technically allow other browser engines, but that does not create a robust browser market.