Indeed. I've never seen anyone I know who is a keen gym goer do wall sits like this. And he's doing that standard ego over form thing by adding weight.And there we have Dave doing wall sits - BADLY
the key to wall-sits is that you form 2x 90 degree angles - at your hips and at your knees. Feet should be around 2 foot off the wall.
he hasn’t formed the correct angle at the knees. This position and leg angle transfers the force to your lower back on the wall, instead of giving you burn at your quads.
an in person training session would have ironed this out long ago.
I don't hate gym noobs but I do hate people like Dave who act like they know it all when their form is awful. He's lucky he hasn't done himself a serious injury yet.