So one of them is missing. Is this just a file upload gone wrong or is one of the dumps actually missing?
The second comment on that page by Stu Thompson:
was left on May 2nd, 2010 at 1:49 am so it was already named "June" before it even was "June".
Therefore, it seems the "May" torrent was simply misnamed.
Conveniently, Stu also has a page for every download, correctly named:
complete with stunning mascot.