Plants don't need complete dark to flower; ever been out in the woods on a moonlit night?
It can get quite bright out there at night, especially if you are in an area where there are no tall trees, just small bushes or open country.
There is an old internet cannabis myth that light leaks cause plants to hermie.
Bullshit, light leaks don't cause hermies.
I haven't had a hermie for many years, they are not common unless one is growing bagseed, which may have come from a hermie plant anyway.
I read a lot on internet forums about people getting hermies, I sometimes wonder if they are just new growers who when a plant turns out to be male they think it's a hermie.
I have just grown my first two feminized plants, they were freebies, as I don't by feminized plants, and while feminized plants have a reputation for being hermies these one's were not hermies, just like normal regular female plants.