To be fair, the previous lab they found in California was I believe found in 22 or 23. So it's been known for a few years that this had been happening.
I could be wrong but I get the sense that the issue here is more fraud than anything nefarious like spreading diseases. The guy running it has a history of intellectual property violations.
Private citizens should definitely not be running unlicensed biolabs and this seemed like it was pretty sloppy (a lot of the kits and samples were degraded and ineffective), to the point where the workers were getting sick.
These types of mice are apparently commonly used in legitimate biolabs for research purposes. My guess is they were used to test whether the testing kits were effective.
It's definitely not good that these labs were / are operating under the government's noses, but I also get the sense that the poster on X was framing it a little disingenuously.