So there are two aspects to reconcile the solid and fluid parts together. First, just like a superfluid, a supersolid can have a portion that flows and one tha

So there are two aspects to reconcile the solid and fluid parts together. First, just like a superfluid, a supersolid can have a portion that flows and one that doesn't (the normal fraction). The second part is that, as you rightfully mentioned, holes are just vacancies in the structure. Here the vacancies in the crystalline structure they made are able to flow along the solid. But as they flow, the structure retains its shape. And at low enough temperature, these excitations condense into a macroscopic quantum state which makes them a superfluid. So in a nutshell, you have an organised structure like a solide, but a portion of that structure flows without breaking the overall structure.