what he is saying is true. a natural female that produces female pollen to ensure the survival of its species(self-pollination) will produce feminized seeds. some say they are more prone to hermieing when stressed though. even a stress induced hermie female will produce female seeds, just more prone to being hermie.
the jist of this is, if a NATURAL female that has went into sex change due to enivronmental factors, lighting interuption, etc.(for a viable reason) produces seed, they are all 100% female. they do not sprout male. they are however more prone to end up as hermies.
if the plant has went hermie for no explainable reasons, the seeds produced by it will be 95% hermie rate.
a way of producing feminised seeds called Roderization or something like that. where breeders have a batch, and they stress induce hermieing. the females that dont hermie during this process are called the true females. they are left in flower around 2weeks longer, and they hermie and self pollinate, or the pollen is used on another natural female, creating very stable feminized seed. there is also the Colladial Silver method.
if you produce seed from a plant that hermies during the stress, they will still be feminized, just not as stable, and they can possibly have a high hermie rate. ive seen good nugs grown from hermie seeds though, so it all depends on the strain you are working with and how stable it is.
EDIT: I am currently doing a experiment for next summer. i got a batch of 3 females which i plan on hermieing. collecting the seeds, labelling and growing them in a specific area as a test to see if they can grow decent bud.