I think the iOS application (the one for Iphone and Ipad) Xmind Cloud is a misnomer. Okey, it does save the maps in Xmind Cloud (Xmind Inc.'s web service), but since you can edit and view those maps directly in a web browser... Perhaps "Xmind for iOS" would have been too dull.
Anyway, the iOS application saves to the web service Xmind Cloud and if you choose so, the desktop application will do the same (when it works, there has been issues). Neither uses Apple's Icloud which is a totally different web service. Of course, you can save your map in the desktop application to Icloud and you will see the file in the Icloud drive application on your iOS device, but you can't view nor edit it there.