The problem, according to a blog post at the Dev-Team Blog, is that versions 4.0.2 and 3.2.2 of iOS was released solely to plug the method the group had used to jailbreak iOS 4.0, and the group doesn’t want to directly fight Apple in an escalating arms race.
“If the cat & mouse game escalates too quickly,” the group said, “especially during beta [Firmware] periods, nobody but Apple benefits. For this reason, there won’t be a 4.0.2/3.2.2 jailbreak specifically during the period where 4.0.2/3.2.2 is the latest public release. At best, some future 4.1x FW jailbreak *may* be compatible with 4.0.2/3.2.2 (but don’t count on that).”
The jailbreak technique the group developed for iOS 4/3.2.1 depended on a security flaw in the way the OS dealt with PDF files. In addition to the jailbreak the group released, the security hole could have been exploited by malicious hackers to take over an iPhone. Apple quickly released a patch for the PDF security hole and released it as iOS 4.0.2/3.2.2.