ok heres the scoop on feminised seeds.
a feminised seed is created by taking a solid female (one that is not going to hermie naturally) and forcing it to hermie, then collecting that pollen and pollinating another female plant. what this does is it pollinates with 2 X chromosones, the only way to get male offspring is to have a XY chromosone, naturally this occurs when a male and female do the deed
but when you force a female plant to make male pollen that pollen does not have the male chromosone therefore cannot produce male offspring.
im no genetics master but this is the "General concept" you can look more into it by googling it there are alot of threads out there that explain how feminized seeds are made.
i actually was thinking of someday trying my hand at thios process but that wont be for a while.