Well it is definitely possible to have the full windshield iced-up, I’ve seen that even on aircraft with windshield heat although very rare. In MSFS even light icing conditions will immediately ice up the whole windshield. So yes not impossible. I might need to rephrase that, what I mean is that it won’t look like MSFS because the type of ice is wrong, in MSFS it looks like a kind of frost which you would expect to form on your car overnight. Not on an aircraft during flight, it will be more like a kind of rime.
And then there is the cockpit side windows and cabin windows icing-up in flight when you turn the windshield heat OFF. Those windows are not even heated in the first place (cabin windows at least) and won’t pick up ice in flight, same with the side fuselage, side of the vertical stabilizer, top of the wing (unless in severe icing). And again it all looks like frost which you would expect on ground, not in flight.