Mozilla is unhappy because the use of browser engines other than WebKit will be restricted to the EU, forcing them to develop two different apps.
For an independent browser like Firefox, managing two browsers is not easy, so it can be forgiven that this could be seen as almost harassment.
Also, the fact that the use of browser engines other than WebKit is limited to iOS means that the use of WebKit is still forced on iPadOS, which also increases the effort for Mozilla.
Every Apple mobile app only runs on Apple hardware. Unless you assume 100% luck or 100% foresight, which is rare, every app that runs on a different platform was written for that different platform in addition to the Apple one.
Where did I say that you can run ios apps directly on Android or osx dmgs on Windows? I never did, I said they almost always have versions of it that run on different platforms. There is a windows version of Photoshop…so your logic here is that osx version of Photoshop cannot run on Windows…no shit…