If this is correct, then it is expected that it will be very hard to produce good samples, because when impurity atoms are introduced in a crystal it is very difficult to control the final positions of the atoms, when there is little energy difference between alternatives.
Minor differences in heat treatment can cause great differences in the electrical and magnetic properties of the samples.
So it is likely that some time will pass until we will know for sure whether this material can be a superconductor, unless some laboratory gets very lucky.
I suppose that the reason why the Korean team was not really ready to publish their results is because they are not able yet to produce material samples in a reproducible manner.
Papers about failed experiments are worth a lot more than no papers about failed experiments. Alas, it is rare.