That's begging the question. The argument for PLOS and Scientific Reports is that in an age where there are no constraints on size of journals, number of paper

That's begging the question. The argument for PLOS and Scientific Reports is that in an age where there are no constraints on size of journals, number of papers in a journal, effort required to sift through papers, etc. selecting for impact is less important than before. Then again, this is not a certain conclusion and there is a lot of room for debate. With extensive searching on Scholar, etc. I Find lesser and lesser need for the stamp of Nature/Science/etc. to certify a paper as high impact.