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.