From what I understand, this is true for indoor growing. For outdoor, I would think it'd be the same. When Fall hits the days get shorter which tells them to start flowering. If any light hits them during this flowering cycle, they revert back to vegetative growth. As far as stunting the growth, this should not a problem since they did all their important growing during their vegetative cycle. During flowering, their growth really slows down so that should not really be a major factor. But to answer your question, yes the plants will go back into vegetative mode.