IMGA rules do basically the same thing, except that the whole of the head (A or B zone) will "neutralize" the target. Your "A+" scoring places a higher premium on accuracy, but in a subgun match or a gunfight I'm not sure I would rely on such hits.
The head as a target A or B is a pretty big target even out at 25+ yards. You might not take those shots personally but many shooters do. Sometimes it pays off and sometimes they end up having to do a followup shot but nothing ventured nothing gained or sometimes they under neutralize the targets as a result of a single B in the head.
There is a difference in the mind set of a person who is looking to get optimal time and a person who is looking to get optimal result. In my opinion the better shooter is a person who gets the optimal result with the best time. If you shoot double or triple shots on the body and the other guy does single head shots in the A+ and your times are tied for that stage who is more skilled?
In some stages you are forced to take those shots. If the designer put some of the shoot targets behind hard cover and only the head or a fraction of the head is exposed then you have
to make those shots sucessfully or you are going to rack up the penalties.