I mean supposedly these are all coming from one source and we have no idea how many of each card there are. There could be several people with several copies of each play test card.
They also could be faked or reproduced. Nobody should be so foolish as to think that these “mounted on card” cards can’t be faked in 2024 by malicious actors.
For all we know there’s former Pokemon employees that have the files and could print new copies of these play test cards and nobody would know any better