In hex map play, every hex is separate. There are no "large" buildings in hex map play. That was added to non-hex play for where there is physically a building that is large, and doesn't have smaller pieces that can be removed. You can remove a 2" area from a large building. Nobody needs to bring a butane torch to a game and cut up their buildings.
In hex play, there's no such restriction. Every hex is its own (small) building. Regardless of the art.