Mark,
I don't think anyone is claiming that a half par hole is one where you would ever write that down on your scorecard (how do you take half a stroke, after all?) I think the concept is pretty clear, its a hole where if you play it properly you have an equal chance of making a par or one less (or more) than par. That's not to say that a short 4 "half par" hole that you think of as a par 3 1/2 is one where you actually AVERAGE 3 1/2 strokes. One or more poorly played shots on some occasions when you play the hole, or tougher conditions will serve to increase one's average.
Half par holes are typically those where because you can reach the green in one or two shots if very well played (i.e., a driveable par 4 or long 3 that's a near driver, or a reachable par 5 or nearly unreachable par 4) Therefore if you are playing well you'd probably have a lot of little chips and pitches where which side of the "half par" equation you fall depends on your short game and putting on that day. Its like a single digit handicap who drives it 300 yards playing a 5500 yard course that's wide open enough that he can play driver. There are going to be a lot of half par holes for him on that course, too many IMHO. You want some of them, but not a majority of the holes you play.