It's just as artificial to make front-quarter shots have no effect as it would be to make tail shots have no effect, or "top" shots (anywhere from top down) have no effect.
You cannot defend that one. Period. It's the worst kind of gamey. Just because it happens to (in your description) lead to better gameplay -- which you cannot prove nor disprove and is totally subjective -- doesn't negate the terrible nature of the matter.