I suspect much of these colonies that get stuck not leaving brood, might be due to the use of standard Italians and not Russian and/or carni bee lines, or acclimatized local survivors.
My lines shut down in a dearth, and going into winter. My experience is that Italians many times will not shut down for anything, eating themselves out of house and home. They will brood right through winter for no other benefit other than a small 2-3 inch patch of brood, that makes no impact on hive survival other than killing a hive as mentioned when bees refuse to move off the brood.
When the Russians were first brought over, some southern breeders used them for a year or two. When they found out that the Russians in particular, would shut down and go through winter with a smaller than normal cluster, it was realized that their use was not in line with what they wanted. They want Italians that brood all year long, and with a little feed in December or January, will have the colonies ready to shake bees from in early February.
It is also this brood break in the summer dearth, and again going into winter, that adds to the Russian strain being somewhat more mite resistant compared to the Italians that never shut down.
And no, my bees do not start at the top of the second box going into winter and remain there all winter. Of course, I don't lose bees due to not moving off brood. And I don't use Italians raised in the south and genetically more in tune with warmer climate dynamics.
Talking about dead bees and why they don't move off the cluster means little unless you understand why that happens and what you can do about it.
BTW....a sealed hive, void of top entrances and a constant break of the propolis seal by the beekeeper, allows bees to deal with issues better. Having top entrances, extra boxes on the hive beyond what the bees need, all play into the little things that make a difference.
Use more northern hardy strains, understand the bee's natural cycles, and give the same benefits they seek in nature, and you will lose less bees.