I don't really know shit about breeding but the way I understand it is before man began altering wild cannabis genetics, natural selection occurred and it was "survival of the FITTEST". Now, man takes the seeds from the wild and begins to breed with the most terpene, most trichome, and/or most THC producing plants (things that won't really help the plant in nature) and traits/genes that once made plants strong and consistent, are now recessive and no longer expressed in the phenotypes we like.
Now this is where "stabilized" genetics come in. All plants can herm. It's how little or how much stress it takes to induce this that makes it hermie prone or not. I would asume that a "hermie prone" plant would just simply require a particular environment or they react to stress from one condition or another they deem unsuitable.
I just had an air pump die and it took me like 2-3 days to figure it out. I had gu's moondance and DVG gorilla grapes affected. Moondance was fine while the gg turned yellowish and threw some male parts. I feel this is a good example of what I'm talking about. Same conditions, two plants, one stresses and one doesn't. Ones more "hermie prone" than the other..