Eh, I hear people talk about .NET desktop apps all the time and they are understood quite well. .NET (and, frankly, everything that isn't HTML/CSS/JS) may be less used outside of backend use than was once the case, but I don't think .NET is conventionally understood to be backend-specific in any general sense.
Perhaps that's still true in casual conversation, but in the hiring world .NET appears to be about server applications exclusively. At least in my observations.
