I disagree, He's hitting HIGH from the tree not low. Its a trajectory thing. Angled shots are affected by gravity like the horizontal distance. Thats why you hit high when you shoot something that looks to be twenty yards from your stand. Its because from the base of your tree the target is closer than it s on the shot angle. The farther out you go the less its noticable & this might be becasuse of air resistance slowing the arrow but its just as likely that since its further out the angle off horizontal is much less.
The closer you get to the tree the worse it gets. Shoot straight down sometime, you'll be off a foot or so at 20 feet because now gravity aint doing squatt.

Thats what a pendulum does, no? The further you lean over the higher t swings thereby lowering your point of impact.