in my seed making experience, seed from the 2 identical parentals, one run my grow partner insisted on flushing them becuase he was a fool and cared more about the bud he would be smoking even though it was a seed grow, not a bud grow; anyway so those were flushed and the resulting seeds were not as plump and healthy looking....... guess what?? 60% males from these seeds & 80% germ rate
next run, i did no flushing - ended up with nice juicy plump brown seeds ....30% males and almost 100% germ rate!!!
also, I did all the post germination stuff with both batches you are supposed to do to end up with more females
1) some (not too much!) nitrogen in soil bed
2) warm soil bed
3) blue light, no red or orange light
4) over 4" deep pots (Clarke's Marijuana Botany on tap roots and sexual determination: reference to Russian botany study)
and NO STRESS for fist 4 weeks (plant dosnt decide right awya whether to be femaile or male)
so, if the breeder is fully focused producing healthy, nutrient fat filled seeds instead of the hash from th eseedgrow and they dont flush; you'll get seeds with higher germ rates & high ratios of females due to the self supplied nutes in the first stage of life
its is also possible to select parentals that produce more female offspring but that takes work and testing