Fascinating. Wondering how it might work for a top entrance. Also makes me question how the bees are able to ventilate the hive, unless he keeps another opening somewhere with small space hardware cloth stapled over it.
I have seen it several years ago and there might be a thread on here somewhere. My opinion of it is that it probably works pretty well as long as it is relatively new. Once the bees build burr comb or smear propolis over those holes it will allow the beetles access. It is only for bottom entrances. The point of the tapered/bent holes facing downwards is that the beetles cannot crawl over that lip without falling. The beetles don't fly inside the hive so they can't gain access. The bees being bigger can get around the lip on the holes.