Many apps are available exactly the same on Android as well, and nearly all apps have at least some equivalent on Android. The fact that an iOS app isn't literally compatible with Android, you can't take the exact same binary and use it on an Android phone, doesn't mean that iOS is a separate market category. You may as well say that UPPAbaby strollers are their own market category because UPPAbaby stroller accessories don't work on other strollers.