Probably misremembering, or it was simple TV hyperbole; it's fairly easy to seal up a hive for transportation so that the bees cannot get out. Hives do "swarm"

Probably misremembering, or it was simple TV hyperbole; it's fairly easy to seal up a hive for transportation so that the bees cannot get out. Hives do "swarm" though -- basically, vacating their box en masse -- so it's possible that they were referring to avoiding this behavior, which could maybe be induced by having a hive box sealed up for too long.