Your reasoning is circular. You're saying that we know the doors go to a different universe because one goes to the dark place, when we're discussing whether or not the dark place is in a different universe.
There's nothing about the doors in the Oceanview motel that suggest they go to different universe. As far as we know they go to different locations within the same reality, or potentially to the astral plane. The only ones we go through are the ones that go to the Bureau and ones that go to the dark place.
If you somehow played the remedy games and didnt also notice that Alan Wake wrote the Max Payne games which exist too idk what to say.
Go back and replay you somehow missed everything.
From the fan wiki description of the motel:
"The Oceanview Motel & Casino is a Place of Power connecting between various different locations. The Federal Bureau of Control theorizes it to be a gateway to alternate dimensions and Thresholds. "
Go back and reread your own comment where you missed the part that explicitly states that at best, characters in the game theorize that it could connect alternate dimensions and thresholds, though once again, the alternate dimensions seen in control are dimensions like the Astral Plane, not an alt universe like EEAAO.