According to the pre-print, these researchers are based at "Naval Medical University, Shanghai, China" - a country with a terrible record of human rights violations and an even worse record when it comes to animal rights. Of 3,000 people surveyed in China, approximately 2,000 hadn't heard of the concept of "animal welfare". I'd be surprised if regulation on non-human animal experiements even existed in their jurisdiction.

Sometimes I wonder if Chinese scientists are going to make scientific advances that Western scientists won't, due to weaker ethical constraints enabling them to perform experiments that Western scientists can't, or lesser regulations enabling them to get the same experiments done faster and cheaper.

If only they had accelarated a COVID-19 vaccine by a few months via human challenge trials.

Yes, I'm saying, in the US, where we may pride ourselves on having standards, there are some lab animals that are exempt, and so I think there's a blind spot, where nobody (in the sense of the lay public) thinks about what's happening to them.