The samples came from a population considered to be at risk for exploitation. So that raises a level of scrutiny.

The researchers having ties to “public security” (police?) adds some credence that maybe there could be a conflict.

“uncovered inconsistencies between the consent documentation and the research reported; the documentation was not sufficiently detailed to resolve the concerns raised”

This to me sounds like the research used the blood in ways and for purposes that the consent forms did not specify. If you consent to foo and bar are they then considered to have consented to baz? That is what that statement sounds like to me.

Another retracted study appears to be because the publication has taken a stance to not publish that kind of research, “genetic forensics” which to my understanding is an area fraught with ethical questions.

I think the overarching issue here is that China hasn’t yet proved that they deserve the benefit of the doubt as it pertains to their handling of the ethics of these studies. In fact the mounting evidence says otherwise, which is why there is extra scrutiny.