Shooting someone in the head, not a headshot

Why is the head hitbox so buggy that the head is embedded somewhere in the chest?

Your bullets going over his head. At 0:33 you can see the bullet land far behind him. In the illustration above, the target's head would be on the line of sight line (to the right of the line of sight arrow). The bullet would follow along the parabolic path and sail clean over your target.

bad hitboxes + you're not compensating for drop

I think half the avatars you shot at had already just been killed by someone else.

if he wasn't compensating for drop, the bullets should have hit them in the chest or legs. He's not compensating for something and it's the opposite, bullet rise.