Arxiv paper with lots of revisions and changes made to subject matter; shouldn't Arxiv clean this up?
It does indeed look confusing and irregular. Oh, and it only gets worse once you start looking into how interrelated it is with different versions of some of his other arXiv postings... In an ideal world, perhaps arXiv should clean this up somehow. However, the moderation team is relatively small, works on a voluntary basis, and has to handle a lot of submissions every day. One really can't expect them to sort out messes like this one, nor do I think it'd be good for them to have an extensive editorial function. Assuming the initial submission meets the criteria, the onus is on the author(s) to communicate clearly - not on arXiv.

It's also worth noting that only the first five versions are included in the daily listings, so individual authors making lots of revisions don't necessarily impact the community too much. Given all this, I think it makes sense for arXiv to focus on rapidly processing new submissions instead of worrying about excessive changes to a (presumably) small number of postings.

Finally, I'll note that in cases like this it's a very good thing that arXiv stores all versions. You can cite a specific version and leave it at that.