Someone should fact check this, but my assumption is that lupulin production and seed formation will occur as separate stages of flowering. Flowers run a set cycle, and they don't necessarily stop flowering just because fertilization has occurred. Once that window closes, senescence occurs and the flower dies, leaving only the seed pod to develop. If fertilization does not occur, some flowers will develop infertile seeds, while others will simply drop the whole pod. It's very likely that hops follow this pattern, and it doesn't matter if fertilization has occurred or not as long as harvest takes place within that window. Someone should fact check that, but I would put money on it.
Also, basslake, upon reflection, I want to recommend that you baby the free hop plants you got. Even if the roots are still in good shape, they've probably still lost some viability. So, I would lightly fertilize them once they sprout, and definitely pick off any flowers that appear - this is going to encourage good root development.
So, I should totally do a Master Gardener program, but I'm so lazy.