Not a myth. What’s inside the fridge doesn’t really matter when talking about efficiency. It pretty much only depends on the rate at which energy seeps into the fridge from outside. All else being equal, chest fridges allow significantly less heat transfer through an open door than regular fridges, and are therefore a more efficient design.
You’re completely right about the second part, though. It’s just not practical, and the fact you would have to keep the door open longer while you rummage around for stuff renders the point moot anyway.
Did you only try F2? It’s possible the graphical session is on tty2 - see if ctl+alt+F1/ 3 does anything