Not always, but sometimes they will swarm for a supercedure, especially if they are in a crowded condition. I agree, with ten cells, it seems like swarm. Maybe you gave them some more space when you removed the queen cells?
what made you think it was efb in the first place?That does not look like EFB.
insufficient evidence to call out efb, it may even be one of the least likely."checked this hive yesterday and found a nasty laying pattern"
from first post