This is one of those things you'll have to find out for yourself. As you're seeing, some will say no light leaks while others will say a little bit won't hurt. I feel it's fiction that light leaks cause hermies, because as you said they're not in complete darkness outdoors. That would mean EVERY outdoor plant would be a hermie, and they're not. Light leaks will slow down the maturing process of the plant though, just like moonlight causes outdoor plants to take longer to mature.