It seems like another overly complicated way to explain something that really is a lot simpler in reality. The fact that a desk appears smooth doesn’t need a fracton to explain it. If you have to make up pairs of particles that appear and then annihilate each other, you don’t really understand what is actually happening. A simpler explanation is probably closer to the truth. A desk seems smooth because we perceive it that way.
They aren’t trying to explain why a desktop appears smooth. That is merely a macro/micro distinction. They are attempting to get closer to an understanding of the gaps in the Standard Model and Quantum Theory.