I've read about bees getting 'demoralized' when you put an empty brood box before they're ready for it...but when someone actually said it out loud at our club meeting last week, it sounded downright strange.

I'll assume that when one says "demoralized" they actually mean that it is somehow detrimental to the colony to put an empty brood box on top of a small colony. If you keep the entrance reduced until the colony is strong enough to defend it's turf, how could the presence of an empty brood box up top be, um, demoralizing?

It can't be a 'keeping warm' thing, since bees stay warm (when necessary) by clustering. it can't be a "more space to defend" thing if you have an entrance reducer in place.

When a swarm moves into new space, it obviously moves into space that is, at that moment, far larger than they can use. How is putting on a new brood box 'prematurely' any different?

Maybe I'm missing something??