What does that have to do with anything? Alleria doesn’t use the “light” just because her husband does, and Turalyon doesn’t use the void, in fact Alleria deliberately turned away from the light in favor of the void’s powers, where she was warned by the Naaru that if she continued down that dark path, the light could not help her.
Any High elf joining the “Void” elves is going to be doing it for the same reason. Their interest in the “void”. Any elf devout, or penitent in the light would never turn to the void - Heck just go listen to the sermon between light and dark in Shattrath. Different ideals, and conflicting magic.
Your argument is a reach.