if you were talking about a meter long segment of pure LK99 you'd have a point. But the pieces in question are so small that even if the LK99 were just copper

if you were talking about a meter long segment of pure LK99 you'd have a point. But the pieces in question are so small that even if the LK99 were just copper their resistance would be so low that experimental error in a casual test would be substantial compared to the resistance. Measuring the resistance would also be frustrated by the superconductive material being scattered in the mass separated by highly resistive impurities, making it easy to get a false negative.