Seeds in bud are very growable.
I started on bagseeds from high quality stuff my friend had- every so often he'd find a couple seeds in a zip and save them for me- I bred the ones I liked and when I got some good afghan genetics, added those to the mix. I don't have a herm problem either.

Immature? You have to judge the maturity of ANY seed- yes, I've gotten seeds from PURCHASED seed packs that weren't fully mature. Plump brown seeds are mature.