Lol I might catch slack for saying this but it really doesn't need to be completely dark. You just can't have useable light hitting the plants. After my own growing the last 14 years, and watching many others grow. I really do not believe that SMALL light leaks, or minor ambiance(like moon light) will cause any issues. I think that typically this is an excuse for hermies when nothing else can be figured out or when growers don't want to accept they messed something else up that stressed the plants. Not to say that perhaps certain phenotypes couldn't be more prone to these variables, but the moon is pretty damn bright for almost half its cycle.
I ran my room for years with the bottom of my room door open to allow air flow. I never had issues with hermies or anything else because it was just a small amount of light that was bouncing off the floor and never reaching my plants. The room was FAR from dark, but the plants still started flowering in about 7 days, and still finished beautifully.
, but that's ok we all started out that way.