It seems to me that trying to calibrate things so that a bullet won't exit on a sideways shot is a bit difficult. It might exit on a lung shot but not exit if one or both shoulders are hit. If it doesn't exit on the lung shot, it might not penetrate enough on the shoulder shot. Buffalo don't stand exactly sideways either, and come in different sizes. You might be 20 yards away or 100 yards away. Too many variables.
Besides, it's altogether fine to study Kevin Robertson's book of photos to see where the anatomy is, but the several buffalo I have ever considered shooting, including the one I did, all seemed to be big black buffalo shaped things standing in the shade, and I could not make out things like the point of the shoulder.
