ive heard this method a few times an i think it does work its also used jus to help garuntee a higher number of females when grown from seed but i dont really like the idea of adding hormones an stuff.
i doubt its got to do with feminized seeds as thats a different process which deosnt have to involve any hormones unless you need mass production of female pollen then it wouldnt be ethryl you would add.
its kinda like giving a human male oestrogen in the way that a bloke would grow tits an other freeaky shit but with plants cos they can produce either male or female plants anyway the process is bit simpler so we jus usually get male or female with the ocasional hermie, in humans you would always end up with a hermie human it would not be physically possible to change man in to a fully fleged woman with jus hormones as are sex is determined from the moment were are conceived, plants however arnt and so can go either way hence makeing sex reversal with the adittion of hormones or sometimes jus undue stress is to some extent actually possible
hope this awnsers it for ya