>But no, there is not anything anyone can do with the critique

Critique doesn't just exist to be actionable.

It can also exist (as in this case) to remind of a possibility. Especially in this case, where the possibility is precluded.

In fact that was the very intended. Pre/post contamination could still have happened, we can't just exclude it because "protocols were followed". Protocols have been followed in other cases where errors got in the way to.

Perhaps you didn't wanted to see a general comment, but somebody spotting a specific error in a specific step of the actual process?