While I haven't heard or read anything to confirm or deny this claim, it could very well be residual fallout from the case of the Ghambian rat carrying monkeypox a few weeks ago. I suppose one could expect the possibilty of pathogens survivng the gassing and freezing of the host only to emerge when thawed at a later date. Many viruses are extremely well adapted for this scenario.
As far as starting your own rat black market, the monetary penalties alone would put most of us out on the street. I believe the greatest damage would be done to the credibilty of the hobby that we seem to have to defend on a daily basis. With the sheer number of immature, vindictive individuals in the hobby these days, it wouldn't take long for someone to "rat you out" and bring the whole well intentioned project to a screaming halt.
My 2 bits
Revenge is a dish best served cold...
With a side plate of steaming entrails,
And a nice Bordeaux!