I didn't want to express that these studies don't take the utmost precautions to guarantee a reproducible and significant result, using animals that are essenti

I didn't want to express that these studies don't take the utmost precautions to guarantee a reproducible and significant result, using animals that are essentially clones of each other and all the things you describe. But at the end, results come down to whether a statistical test found that their findings are statistically significant. They don't exactly try to establish a causal nexus: they admit ignorance over the controlling factors. ATHEIST did just that, run a bunch of statistical tests, and they all yielded p-values lower than what passes for statistical significance in that Nature article.