Well, I don't think they swarmed and they put honey in the top box. Last fall on a questionable temperature day, I separated the boxes and put a screwdriver between them to while I tried to lift the box off. I tried to lift it but that deep full of honey was heavier than I felt like lifting and since I wasn't sure I should be doing it anyway, I just tipped it back down. Glad I'm planning on going to 8-frame mediums!
This spring, I was quite pleased to see all the bees flying in and out, some gathering pollen from who knows where. When a day came I could look in, the top box had bees all over it. And was still very heavy! When I looked in the bottom, it was mostly vacated with few bees and some patches of capped honey here and there. I had looked through half the top box, but didn't know where the brood was. There was a cloud of robbing bees when I put the hive back together. I have reduced the entrance to two bee widths.
A couple of weeks later, there was a tremendous drop of bees flying. I looked in the top box and not many bees on the outside frames. Looking in the other half of the box I didn't look in the first time, I did see a couple of frames with bees plastered tightly to the sides, which I assume was the brood. Now, another week, hardly any bees flying even when it gets above 50F.
I didn't think I had a weak swarm this year, but I don't know what happened. One thought I had is they had the top filled with honey except for the two frames. They moved up to there to raise the brood, but when it turned cold again, the rest of the bees couldn't fit there, nor in the capped frames of honey in the top box. So they were left to the bottom box which had nothing for them to eat. A large number of bees were carried out in front of the hive. So many that carrion beetles are crawling through them.
So, same old question, but different, almost opposite conditions. I could remove the empty bottom box, but if they start building up as fast as last year, there may be no place for raising brood since the top is mostly filled with honey. I tend to be of the idea to leave them alone. Since it's been said they naturally move down, and since they are in the top this year, there is plenty of empty drawn brood comb right below them. Any reason I really should or really shouldn't change something at this point in time?