Board Thread:Warhammer 40k General Discussion/@comment-4851119-20140118095944/@comment-6078851-20140211004108

given the level of genetic engineering available to emps it's totally feasible that he could have made female primarchs, which could be why they were expunged. maybe they just weren't as suited to unadulterated and unending war as the males. or maybe the female of the II reproduced with the male of the XI legion but their offspring turned out to be genetic monstrosities due to the level genetic manipulation within the parents, as well as due to the close familial ties. or it might have been that female primarchs were simply too distracting for the male primarchs :)

again i don't really believe this i'm just throwing out ideas.

as for expunged records, none of the traitors had their records expunged - if they did we wouldn't know of them. their records may have been removed/redacted from many sources, or only be available to a very select few, but their records still exist within the imperial library. the space marine codex shows - 9 legions loyal, 9 legions "excommunicate traitoris", 2  legions "all records expunged from library".

it's there in black and white, and probably on this wiki somewhere too, the only legions to have their records expunged were the II and XI, which really begs the question: given the severity of the actions of horus and friends, why do their records remain while 2 are completely removed? what could have been so bad as to have been worse than the heresy?!?