Recently, I was speaking with a beekeeper and we were discussing the subject of why bees move up into the super during the winter months.
There are several reasons for this happening.
The first reason is that the warmth the bees create in the hive rises to the top of the hive. As the heat rises to the top of the hive, the bees want to follow this heat to help conserve their energy (within the cluster) and be efficient in the hive.
The second reason is the honey acts like an insulation barrier within the hive. Due to the density of honey it cannot change temperatures rapidly and offers the bees better heating efficiency within the hive.
The third reason is the honey is their food source and it is much more easier for the bees to eat and not go far from their cluster of warmth.
Beekeepers should not try to force the cluster of bees back down to the brood box. If this happens, the cluster will have to work harder on keeping warm. You may even lose your colony due to the cluster cannot keep warm.
Ray