I might catch flack for this but the truth has to be told ......."hermies" are almost 100% due to growers' era!!! I know some of us like to think of ourselves as master grower this and master breeder that but most don't have a clue about cannabis plant biology. Stress a plant and she goes into survival mode, period!! Every female is created to produce seeds, EVERY!!! First and foremost they're being stressed beyond belief by growing them for sinsemilla. Some of us feed too much or too little, some of us have them in the wrong kinds of medium, some grow in the wrong type of environments, some have undiscovered light leaks/interrupted cycles, etc, etc. Conclusion, some plants are a little more hardier some a tad or super sensitive!! Hard to grow a sensitive plant without any issues if she's getting force fed and vise versa.
Cannabis is a dioecoius plant meaning it has male and female individuals. A true hermie (monoecious) plant has separate male and female flowers on the same plant, in my close to 3 decades of growing I've never seen an MJ plant like that! What is being witnessed that we call herms is actually polygamo-dioecoius (male & female flowers in the same bud)
Whenever I see a "herm" on a plant I try to go back a week or so to see what I did to it before I toss it ....probably best to run em twice too since these type of plants acclimatize to there growing conditions over time rather quickly.
I've grown plenty of plants from fem mom crosses and barely if ever had any intersex issues, no more than I have with regular beans. The minute we think we know it all life has a funny way of putting us back in our place, keep learning and growing ...they go hand in hand!!