Seems likely his bees, so he would know their temperament, but swarms are generally docile anyway (bees are gorged with honey).
As others said I would not have done it quite like that, but saying that, a quick jerk to drop the swarm onto the hive is likely no worse than into a box. If there were some brood in the box I would have left it once the queen was in and collected it when quiet.
Probably better, and just as easy, to have collected them in a box and run them into a hive body in the evening. No drama and not really worth recording, if done like that.
Regards, RAB