I agree with PCars...
The SP says to set 6,000 feet in the LAND ALT window till either TOD or around 20 minutes prior.
That is to keep the cabin altitude to 6,000 for as long as possible before setting the actual landing altitude in the window, and having the cabin go to a possibly uncomfortable altitude for the pax.
Also, (as it says), if the cabin altitude should go above 9,000 feet (due to the setting of the LAND ALT), it introduces other problems for the crew for longer than necessary, like use of oxygen when the cabin is above 10,000 feet.
That's my take on it...
EW73