Hmm I can’t say for sure… the literature about this is vast and the rabbit hole goes deep 
I don’t remember coming across this paper though.
From what I understand from genetics(very limited) they used the known modes of inheritance classification.
And ran their problem plants through a pedigree analysis
For an added layer of pleasure, let’s say they each have very strict rules and some overlap lol
That’s how they came to the conclusion that our beloved pistillate males were x to autosome.
I tried to get definitive answers about all this intersex stuff and its a crap shoot, “it depends” kind of deal…
A perfect example of this would be peyote purple
This line is feminized but when Charlie first released it, he called it regular due to males popping here and there. There’s a thread somewhere on the internet where him and another breeder talk openly about how he brought the line to 95%+ female(from 75%, I’d guess) “through careful selection”
If you want to read more I posted some links months back about s1 males and such…
I think it’s great that more and more people want to learn about the genetics of our favorite plants 