That doesn't make sense? The jailbreak is PDF based and the device has to be jailbroken in order for you to install the patch, which protects the user from other PDF based (harmful) exploits via the patch in Cydia.
It's kind of silly but no one would have known about the PDF vulnerability until jailbreakme 3.0 was released, it wouldn't have mattered.
To clarify and elaborate: Apple was alerted about the vulnerability when it was utilized in a jailbreak. Since it could be used maliciously, however unlikely that is, Apple released a security update (firmware 4.3.4) to patch it. If you install the update, jailbreakme.com won't work. Since the 4.3.4 update does nothing but fix the exploit, you can have the best of both worlds by jailbreaking 4.3.3 and then installing the PDF patch in Cydia.
Each firmware update throws in a new problem, most if not all recent firmware updates have been jailbreakable, but tethered initially. I see no requirement to update to 4.3.4 when I can get the PDF patch from Cydia for 4.3.3.