If done right and the right plants are chosen then they will be 99,999% female. Most hermaphrodites come up if the parent plants had the tendency in their genes. The reversal is done by chemicals, look up STS (silver thiosulphate).
Thanks for your answers. I prefer regular seeds (old school), not that there's anything wrong with femenized. I like the idea of making my own seeds f1 for my own stash instead of paying the high price of seeds. I know someone has to make a living putting the time and money into the business and definitely appreciate it.