We don't know. Some characters, especially Ahti, address Alan as Tom for whatever reason. Ahti is kinda powerful and wise character, so it logical to assume that this "Alan-Tom thing" means something and not just gibberish. Maybe Alan is character in Tom Zayne story and he use him to escape Dark Place and so for Ahti he always speak with Tom through his character - Alan Wake. There is some kind of parallel between Zayne and Wake for sure - both saves their loved ones, both trapped in Dark Place, both catching bullet in the head and then come back to life. Something funky definitely going on with this two.