Lets assume trailer shows real barnacle as u can find it in game.
If moons are Tidally locked to the planet they orbit, the sun still shines on both sides. Same as Earth's moon. Our moon does not have dark side, it only shows one side to earth but shows both sides to our sun.
Tidally locked moons are not different than others that are not tidally locked. They still have day and night cycle.
Tidally locked planets have dark side but i don't know if there is one in the nebula with high gravity. Has anyone checked for tidally locked planets with high G in the Pleiades ?
The best way to narrow the search is to find tidally locked planet with roughly 1g high metal content or rocky world and search only the "sunrise" (edge between dark and light side) because only than dust can exist i think. That should narrow the search quite a bit.
But everything i sad above can be wrong there is noting stopping a GM spawning one where he is at. The trailers are meant to be good for the eyes.
And also dark scene shows better the colors of the structure and adds mystery so also dark side of the planets could also be wrong

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