I don't limit the brood chamber and as a matter of fact, they actually decide what the chamber is as I do not run an excluder. Here where i live we don't get really cold albeit we do have cold snaps and to me, in my opinion, double deeps is overkill although i wont restrict where she goes, I let them handle that on their own...but thats just mePersonally I would be running two deeps or the equivalency there of no matter where I lived. Why limit the brood chamber?
So each must decide which way to go, neither actually hurt anything. IMO