"Published" in scare quotes. By definition, preprints are not reviewed. It's like a Wordpress for scientific papers. It was created so that researchers could get their work out to their peers quickly rather than waiting for the necessarily long review process. Or mass mailing PDFs.

Unless the author(s) of something on the arXiv is established, and the paper says something like "submitted to so-and-so journal", you should take everything in arXiv with heaps of salt.