Hereward just want to give you a heads up.
BuckGodot pointed out that my Propaganda Center mod isn't usable by the Drengin or the Yor because they don't use ColonizationTech, they call it ImperialismTech or PropagationTech respectively.
At which point I realized that I had used ColonizationTech as the Prereq throughout Planetary Diversity. Which explains why I was getting anomalous behavior out of the Drengin with regard to my pseudo-extreme worlds.
So long story short I seemed to recall you mentioning using ColonizationTech on your Planetary Traits mod and when I checked sure enough you are.
I am planning to switch mine to use TechTree which is the GenericName for all tech trees and is used in lots of Prereg's throught the game files.
So thanks to BuckGodot for the heads up he's a lifesaver!