Dispatchers are the same only for iOS, not for Android.
ktorScope uses GlobalScope (not recommended at moment) that allows you to define global coroutine for background work. By default, GlobalScope uses Dispatchers.Default. It's ok for Android, but in iOS we need to specify all dispatchers by ourselfs. And we have to use dispatchers queue main, because dispatchers queue global (any qos) is not bound to any thread.