they do. they bones control the cage mesh. before to maintain volume of your character mesh, you would bind latices to the bones to control your character mesh. but that wasn't a very elegant solution as latices are box shaped and your mesh is arbitrarily shaped. also latices have a bunch of interior points that need to be dealt with. so people used multiple latices, one for each limb, one for head, etc. then you had to make sure the latices overlapped nicely and played nice with each other. this new method uses an over sized low res version of your mesh. much simpler. it also accounts for things that are a pain when binding your mesh like finger joints. where your middle finger bone might affect some of your pointer finger mesh.

the video from the paper explains it pretty well https://www.youtube.com/watch?v=egf4m6zVHUI