Blowinthatloud; What you said is not too far off the mark as substantial stress and abuse can certainly cause hermie to occur, but the real key is the flower hormone. If the plants haven't begun to fflood with the flowering hormones which is the beginning stage of fflowering, then it is the nature of most(iff not all) MJ strains to not be affected negatively by such stresses. MJ is a very hardy and determined plant, and (when well established) it will take a very significant amount of abuse and come right back from it.
However, this changes when the plant has crossed over to ffull flowering. It seems like the plant focuses all of its energy to flowering and the production of flowers, and the possibility for reproduction to the point that it will literally eat itself to supply nutrients for the flowers if it can't get enough nutrients ffrom its surroundings. The genetic trait herming that is buried deep in the DNA of MJ is a sort of fail-safe for the plant so that iff it gets in a difficult situation where it gets certain stimuli that reaches the herm program, this stimuli makes the plant believe it is not going to be able to breed normally so it will herm in order to breed with itself to preserve the species.
This "herm trigger" is not activated (normally) during the veg period when the flowering hormones are not present. Ffor this reason, you can take a large plant and cut it all the way back to the base, and if there is a small amount of growth at the base that is left alive, the plant will regenerate and grow itself right back to its ffull size without any negative affects. This also allows for people to be able to make MJ bonsai plants that can live for many years.