It all makes sense to me . Its the same with a windsurf sail . Shape of the sail is supper important to performance and how the wind catches the sail and holds in there then releases . Actually when surfing sales are more high-performance the most sailboats up to the race boats where you can trim the mast.

I get the outboard sheet idea, but it's not very well shown here... maybe a diagram would help?

I love the idea, but in the video he's cranking a blue line, and easing off a pale coloured line. When the shot moves to the clew, there's no blue line. I'm a bit confused as to what's going on tbh