Hi Christoph, sks.pod was changed in 1.1.2 to fix this in the man page. I checked and it had been ommitted from the output of 'sks help'. The last part is committed and will be pulled into the trunk for the next release.
https://bitbucket.org/jpclizbe/sks-keyserver/changeset/b757f2895aca Commit message: Clarify description of 'sks dump' in 'sks help' output. This was overlooked when sks.pod was updated to close Debian bug #600194 New text reads: sks dump numkeys dumpdir [prefix]: Create a raw dump of the keys in the database. The dump is split into multiple files containing numkeys keys per file. Optional prefix is added to each dump filename. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org