my experience is you can take that 'total darkness' with a grain of salt. but I'm an outdoorgrower, they might be more sensitive to it indoors.
the theoretical part why lightleaks could cause issues is all right(look into phytochromes), it's not just weedgrowermyth.
the question though is of a small lightleak is intense enough to be sensed by the plant.
common sense tells me no. my outdoorplants have never had issues with the moon, stars, a somewhat nearby streetlamp or light shining trough my window onto the balcony. I've only had revegging plants from planting early strains out too early, so they get triggered while the days are still getting longer, and reveg due to that.
and there are plenty of other plantspecies, that also are influenced by daylength and using the same system to sense it, that grow fine outdoors, even in cities with plenty of streetlights.
I've also forceflowered plants using a pretty macgyver/ghetto setup. take plant inside, put it in a closet, and hang a blanket over the door to mostly block the light coming trough the crack(the door doesn't close well, and there's light coming trouh the gap caused by the hinges). and it has never failed me, no hermies due to lightleaks either.
although I can think of a few reasons why it might not be as bad outdoor as indoor:
-acclimation. maybe because outdoorplants always receive some light from stars and the moon, and light pollution from humans, they get desensitized a bit
-intensity. even if the moon seems bright, the intensity hitting a leaf might not be that big, and we see the moon at night when our eyes are adapted to lower light, so it may seem much brighter than it actually is.
-color/spectrum. streetlights and lamps in our houses are usually more yellow, since that's the light our eyes perceive best, and it's a pleasant color. while plants mostly use light from the blue and red parts of the spectrum. so a light could seem really bright to us, but if it's mostly yellow it could seem a lot less bright to a plant.