I understand that, and I have seen this done with just caught swarms before.
They leave the board 4 inches from the hive entrance, in a hive that has built swarm cells, but has not swarmed yet. The bees that were preparing to go with the swarm, will not "jump" the four inches to re-enter the hive. Are these bees that were going to go with the swarm, really young bees that have never flown out of the hive?
What would be the advantage of doing it this way as opposed to a walk away split? Would it be that it mimics the swarm exactly the way the hive had it planned, and splits the bees accordingly?
when the bees swarm there is a mix of bees in the swarm-young and old-the Russian is using this as a splitting technique -we are using it as a swarm prevention technique -the Russian is reading much more into this than there is-the Russian
is using this technique as a way to harvest a CLUSTER of bees from a hive-for his split-there is nothing magic about the bees in the cluster that forms at the gap he has created between ramp and hive-body-and it is very possible to end up without a queen when he harvests that cluster-and if given time the bees dont jump--they make a link and will daisy-chain
across the gap-there is no value to this technique for splitting --only to provide FALSE swarm for SWARM CONTROL --