Swarm cells are many times triggered by an instinct of nature dictated by flow, and not necessarily on sole factors such as strength.
And some bees, such as AHB's, will swarm up to 18 times a year in warm climates. Strength has nothing to do with it. It is perpetuation of the species and predicated on programming over millions of years. And one of the strongest factors in swarming is flow.
This can be seen in the fact that 20% of all swarms in the northeast is done in September and on the fall flow. Why would bees cast off swarms in September when such swarms have absolutely NO chance of surviving? Mother nature is not that stupid. But she is programmed sometimes. And so we take warm region bees, put them in the north, and they are still programmed to swarm upon flow stimulation. And like magic...they swarm in September.
Just something to consider.....