In mobile, if it's trying to download on Data, it will stop and tell you that it is waiting on WiFi, or you can download X MB of data now, and give you the option to download. On Desktop, it won't let you know how much you're downloading. Seriously messed up there. Many, many people have data usage limits even on wired LAN, especially if they are on Satellite Internet service. However, Microsoft seems to think the only metered plans available in the world are if you are using a Mobile Hotspot. They have their heads in the sand on that one for some reason.