1) You have to restart the phone to activate the patch. Many users might not have restarted in ages, and this alone would cause a good performance gain.
2) The patch is keeping the CPU from idling by constantly writing to /dev/random. This gives you better performance at the detriment of battery life.
3) Placebo effect.
My suspicion is that it depends heavily on the CPU governor [1] a device uses. Some will see that process running once a second, and keep the CPU at or near max frequency 100% of the time. Others will back down more quickly and you won't see much of a benefit, and still others were probably running at max frequency even before the change, so it wouldn't have much of an effect on them either.
[1]: http://androidforums.com/xperia-mini-all-things-root/513426-...
From what I can tell, this is the technological-age incarnation of superstition.
I can say, though, that I've not felt any difference on the devices would benefit from it in the performance department, however.
Good points, though.