It adds space for a disabled space.
Just looked around, there is NO disabled space in this carriage - also on a 165 I'm sure the disabled space is not in both carriages? And why have them in first class - there is no difference in leg room/space - just lack of a horizontal surface at table height
And as I said, I measured the space! There is no difference..... (I have a tape measure on me as I was up at my mothers helping her measure for some new furniture!)