I think its qiute a normal thing for the plant to do when late in flower its like a built in survival thing so that if the plant isnt pollenated at the end of the season it can carry on the species.
I have read that if its a genetic hermie it will herm straight away not at the end, what you got is a female thats late hermie or something like that, dutch passion deliberatly late stress plants to herm to create fem seeds I think they get the pollen sacks from one plant and use that pollen on a clone of the same plant, I cant remeber excactly how they do it.
with the big bang i had it didnt herm at all I did not find one seed init but i didnt look all the way thru it all, and there was a light leak. so it that respect the genetics were good.
I have a load of late herm seeds i have collected and I'm going to grow, i think they will be ok