[koops65]

I think every complex is a unique case, and the editors, along with the illustrator, can decide if or how to break it up into separate components.

I believe a big part of it has to do with the part of the world the building is from. Hong Kong seems to be able to have multiple towers on a single base, while Toronto doesn't do that, unless the towers are joined together higher up above the podium, such as a sky-bridge.