I have seen the same sort of thing happen quite often, both with southern kudu and Cape kudu--and a lot of other animals as well. The truth is that very few hunters, guides, PH's etc. can call inches very closely. Part of this is due to different body sizes of animals, and part of it due to configuration of horns.
As an example, a couple of years ago I hunted elk with a top outfitter in New Mexico. The very first morning he and I ran into two bulls unexpectedly, only 100 yards away in scrub oak brush above us. "Shoot the one on the right!" he said. I'd already had the same thought, and my rifle was on the way up. I dropped thye bull with a high shoulder shot, and he was a fine bull--but scored about 15-20 points less than the outfitter had guessed, because of somewhat short main beams. I didn't give a damn, mostly because I don't score animals anymore--but he did.
My hunting partner went 5 days looking over a lot of elk, his guide thinking none were big enough. The hunt was coming down to the wire when the outfitter and I found a nice bull feeding across a canyon. We went and found my partner and his guide, and they made a late afternoon stalk on the bull.
The outfitter guessed the bull at under 300 points. I thought it was over 300 but kept my mouth shut. My partner's guide thought it was around 300, but my partner had never shot anything bigger than a spike before, so they made the stalk, and my partner made a nice shot at over 300 yards.
Turned out the bull had a HUGE body, and scored just under 350. Part of the problem was that he was all alone, with no other bulls nearby, even long after the rut. Another problem was that he was grazing on a snow-covered hillside, and the glare from the snow made his heavy antlers appear thinner.
All I know is that after I decide pull the trigger, I'll be happy with the result.
