The are actively responding to a possible intrusion and are therefore not motivated to give away specific details of the attacker's techniques to either the attacker or other hostile parties.

The MD5's you want are specific to the kit used to attack their client and would disclose the effectiveness of their response and investigation to an attacker,and are also not much good to anyone else. In the Disqus comments the author offers to provide them on request from legitimate researchers.

This is a standard precaution, not at all bogus, and it is great that they were able to share as much as they did for general use.

A better explanation is provided down-thread on the article's comments page. The author comments are overly laden with PR-ese, but there's not much you can do with MD5 hashes of files that are customized per system anyway. Since this rootkit modifies system files and doesn't alter the kernel to hide itself, standard rootkit detection tools will find it.