Do races that have Low Light Vision also have eye-shine? In more technical terms does natural low light vision come from possessing a tapetum lucidum?
Nobody else seems inclined to answer, so I guess I will. This game isn't science-based. Things do what they do because they say they do it. There is - to my knowledge - no lore, backstory, or explanation as to how low-light vision (or darkvision for that matter) happens. It just does. GMs are left to fill in the blanks as they see fit.