Every author named as writing a paper bears full responsibility for the paper.
This has the nice added bonus that it will likely catch PI's that put their name on their grad students paper without actually doing the mentoring they were supposed to. It will also catch professors that coast (or at least inflate their citation index) by getting their name on papers they barely contributed to.
I am quite convinced that, under these arxive guidelines, every single major PI in the field will be banned within a few years.
Catching a lot of PIs that have allowed and even encouraged slop submission is a good thing in my book.