Of course, the major challenge with a human arbiter instead of the computer is that the unit who's ass is getting kicked will default to the excuse of "That idiot running the exercise didn't give us credit for the # of (fill in the blank) that we should've had! If we had that this would all be different!"

It's the same reason we don't use false positives in the intel training - it allows the unit to have a built-in excuse to ignore the lessons they should've learned.

If you've got the computer to point to and say "you fired 20 shots and 11 hit" the unit doesn't argue as much as they would if there was a 'DM' saying the same thing.