Honestly, just send out the samples and have people verify the claims. Demonstrating Meissner effect can be done by a grad student, especially if you don't need a pressure cell or low-temperature setup.
It’s obvious there’s a limited number of samples and they potentially don’t feel like they have a complete grasp on how to reliably produce more using their current level of knowledge regarding the process they used to create the first one… sometimes science involves luck. They have been working on this for years, I can completely believe a non-trivial portion of that time was spent trying to go from a fluke to having at least some ability to produce samples that demonstrate superconducting properties.
They may have only a half dozen samples of varying purity and quality…
The samples may not be particularly “strong” and given the powder based process involved may be too brittle to safely “send” and thus require careful hand courier delivery like a fresh organ for transplant, just without the urgency…
It’s entirely possible they may be mistaken and it’s not a superconductor, but these people are not fools, so I’m inclined to “give them enough rope” and to let this all play out and see where the either falter and the falsehoods exposed by the absence of any further evidence, they are are shown their mistakes once others get their hands on samples, other’s reproduction proves them correct, or their samples are studied by others and the evidence from their paper proves to be correct regardless of novel theories regarding the mechanism of superconductivity involved.
Science is a process, and to be honest it’s fun watching how fast people are pouring on the gas and trying to find out if this is real or not … stark contrast to the abject scepticism and shoestring budgets given to many innovative potential ideas.
I hear what you're saying, but it's not like the sample would need hand couriering a great distance. They're in Seoul, home to a large number of universities [1]. If the discovery is real then I'd hope another university there validates it soon.