> Not how to read various buttons as on or off.
That may not be explicitly trained, but it's heavily trained becasue they must get that right to pass the tests. If they misunderstand at first, they won't for long. Also, the user is highly motivated - they don't want to crash the plane.
Consumers are often looking at UIs for the first time, and are highly motivated to go back to their feed and see what they missed.