My view of the video seemed much simpler -- and more avionics not really the key answer. They seemed to be running the front of the cloud with an easy out to the right, into the wind. There was a moment with a bit of leftward V shaped notch in the clouds, which they followed downwind. Then it sounds like the instructor got confused, and rather than turn right, follow the V shaped notch back to the right maintaining the path to the valley, they chose to go over the top of the clouds, with building cloud to their right. I was leaning to the right while watching! Clearly this brought them to the lee side of the ridge and a world of trouble. The first and most essential lesson, when flying in such conditions whether ridge or wave, always maintain a clear exit path! For ridge, most likely upwind. For wave, the exit path is often downwind. Perhaps being in the back seat is a tough place to make these decisions too, which require a lot of staring at clouds.

John Cochrane.