"Occasional" Extreme Planets ubiquitous

Hi,

I've just started a game in Crusade 2.21 where with "occasional" Extreme planets but the first five I discovered were Extreme: four required Atmospheric cleansing and the other Extreme Colonisation. 

Has anybody else  experienced this  and does anybody know offhand the definition of  occasional. If it's 0.2 then we're at 1/3125 which is small but would occur with a large enough sample. If 0.1 then we're at /100000 which feels like it's going a bit on the sort of sample size of games played. 

Actually I just used the console to lift fow and there are plenty of habitable planets a bit further away so maybe I was just unlucky? In any case, I've whingily started another game.

Cheers,

Jon