Because if it is superconducting they only have tiny tiny superconducting chunks in a much larger sample that isn't. A couple of superconducting grains of sand

Because if it is superconducting they only have tiny tiny superconducting chunks in a much larger sample that isn't. A couple of superconducting grains of sand in a rock, basically. Separate them out, try to test them on their own while ignoring all the rock parts, well that's difficult. I suspect that what they actually have is some incredibly tiny superconducting crystals suspended on a material that is almost identical except for the placement of a few atoms. Very hard to work with. Or it's just a regular diamagenetic material.