It's not a lazy criticism, if the data is so variable when it comes to various conclusions of the same data set, imagine the difference when it goes from rats to humans!
I would agree, it definitely isn't always a lazy criticism. But to be unlazy it should include something that expounds on why it might matter. When the entirety of the response to the study is "in rats" that doesn't seem helpful to me
I fully agree with your comment out of context, and I think it actually backs up GP's point about not lazily dismissing stuff as "in rats"