What This Means
That said, 400 points is a narrow entry point. The Alaska presence there is limited, and the cabin choice is only Interior - GTY.
The more practical Alaska floor is 800 points. At that tier, Anthem of the Seas shows Balcony - GTY and Oceanview - GTY Alaska sailings, which makes the region much more usable. By 2000 points, Alaska is no longer a special case; it is part of the regular mix with 61 sailings.
So the answer is two-part: Alaska technically unlocks at 400 points, but 800 points is where it becomes practical.