Many popular poly-hybrid strains carry the genetics for the herme trait. I'd guess all cannabis has the genetic marker to some extent but some seem to express it much more than others, i.e. "stable breeding lines". It doesn't seem that the feminization process is what creates the issue. Check out this video of Mr Soul from Brother Grimm. It's a cheesy presentation but a good explanation of the cause for cannabis to self pollinate. It's hormonal.