I agree with your first part but not your second. Most authors do not make outrageous claims, and I surely would reject their manuscript if they did. I've done it before and will do it again without any issue.
To me, the point of peer review is to both evaluate the science/correctness of the work, but also to ensure that this is something novel that is worth telling others about. Does the manuscript introduce something novel into the literature? That is my standard (and the standard that I was taught). I typically look for at least one of three things: new theory, new data/experiments, or an extensive review and summation of existing work. The more results the manuscript has, the more likely it is to meet this novelty requirement.
To me, the point of peer review is to both evaluate the science/correctness of the work, but also to ensure that this is something novel that is worth telling others about. Does the manuscript introduce something novel into the literature? That is my standard (and the standard that I was taught). I typically look for at least one of three things: new theory, new data/experiments, or an extensive review and summation of existing work. The more results the manuscript has, the more likely it is to meet this novelty requirement.