I would have posteds sooner, but Johan's avatar had me spellbound for a while...

Certinly one aspect is imagining where the vital is in relation to the angle - 6 inches deep, a foot deep 2 feet deep. You need to visualize that, and it will in the future impact your point of aim. Bell undoubtedly had this down to a fine art. Yes, the brain is between the eyes on a frontal shot, but unless you are 12 feet off the ground, it is not a straight shot between the eyes, since the bullet follows the angle of aim. So if you shoot between an elephant's eyes at 10 meters, the shot will miss the brain which is a good 2 feet into the head.

The other aspect is that on any high or low angle shot, your bullet will shoot high. Kind of counterintuitive but high it goes. How high is a function of caliber, range, temperature, etc.