Hello 220,, yes I am like located in USA so one could question my input to a person on my the other side of the planet. However, I wanted to point out, in our country, particularly Arkansas (south central USA) we had swarms in November. Very, very late for swarms, almost unheard of. Bees in Our area were acting unusual in 2016 for lack of better words.
You are correct, swarm cells on bottom, not likely a supersedure nor abscond. Maybe your bees are behaving a little unusual like our bees in my area. Late, very late, swarms that I cannot explain other than the bees natural drive to reproduce. I wished I could offer a better explanation, but reproduction may be the simple answer.
I would like to know the age of your prolific queens.
Best of luck.