I can’t help but think of the physics of this…
So you screw your feet into the ground, position yourself so that your tibias and fibulas are perpendicular to the ground, and then put weight on it? Where the hell is it going to go? Are your feet going to go through the floor?
That’s only part of it, of course.
There is a bit of weight being applied to the upper portion of the thighs but if you press yourself into the wall enough you get assistance from that as well.
So whatever weight you think you can apply to your wall sit, you’re not actually supporting that weight.
And on top of all of that, it’s pointless. Research has clearly shown (a long time ago) that isometric work will improve your strength at the specific angle only. You would only improve at sitting in that position because there aren’t any real life movements that replicate that position (you’d fall over).
Lastly, wall sits seem to be good for improving your lactate threshold in your quads… so I guess there’s that?
I’ve only ever done them prior to some man-to-man defensive drills in basketball. We built up to a 4 minute wall sit and then got to play half court defense while the offense threw the ball around as fast as humanly possible. It sucked.