Track 1 has an enormous platform on the south side, but yes tracks 4 and 8 do retain their current platform widths.The platforms appear a lot narrower at places where the track is dead ending. For example, Tracks 1, 4 and 8. Aren't they rebuilding the platforms to make them wider? In this diagram, it looks like some portions of the platforms will be narrower while some other portions wider.
My guesses are:
- On the terminating tracks it is not necessary for the platforms to simultaneously handle boardings and alightings, and there are two platforms available so each one only needs to handle half of the passenger load.
- It's an existing station and there are severe space constraints including adjacent skyscrapers and the existing support pillars under the tracks which severely limit the ability for tracks to be shifted within the trainshed.