I think it's called a reflex viewer. Sort of like Single Lens Reflex or Twin lens reflex.

Have you ever used a TLR? Dealing with upside down and backwards was relatively easy after dealing with the TLR. You need to watch the image and ignore all other inputs. It's easier with a LF camera since the image is so large. If you're under the dark cloth it's even easier. Your brain just assumes upside down and backwards is normal after awhile.