You're focusing on exactly one aspect of peer review, determining whether the statistical methods used were valid, which I agree can be done by pretty much anyone with a background in statistics (given that these days it's pretty easy to get in touch with the authors to ask for clarification). But peer review is about more than just determining whether the paper is internally coherent (or directly lifts text from other papers by the same author, which can be determined by a machine). I shouldn't have to say this, but a former physics Ph.D. is emphatically not qualified to perform peer review on papers on cell biology solely because physics and cell biology are both science. Papers don't exist in a vacuum, and by engaging in practices like selective citation (and others I mentioned in the previous post), it's possible to convince intelligent and reasonable people of a point that is completely wrong. In fact, it's so easy it even happens somewhat routinely within narrow subspecialties, where there may only be a handful of experts on a phenomenon worldwide. People who aren't up to date with the field already usually don't have time to spend weeks, months, or years trudging through the literature to gain enough background knowledge to make those kinds of decisions.