I'm curious about how you would add supers. It seems the roof would just go on top of the super, but they would have to be made for the style so it would blend together.
It's a smaller box that holds shorter frames that will fit on the top of the main hive body. When the bees are at the peak of their honey making it gives them more room to store it. Sometimes beekeepers are able to put several on top of the main hive if the flow is good.
The resident beeks can explain it to you better though.
Good advice @thistlebloom My 1st thought was yes, it is cute, but.... practical? And the cost is much more than plain boxes. Guess they would disguise it from neighbors that are against bees.