feminized seeds com from self polinating of hermies and i believe a backcross after to stabilize. the problem is that if the original plant hermied easily the seeds will have the liklyhood of going herm.
you want a severly herm resistant plant and force it to go herm and then you end with seeds that will be more likely female than hermaphrodite.
a self polinated herm can only produce fem / herm seeds.
i am not sure if pollenating another plant with hermaphrodite pollen will produce only fem / herm seeds .