Those thin windows appear to be on the side wall of east and west facing units, where the main (larger) windows face on the opposing corner of the building. The floorplan is probably identical to those on the interior of the building, so those thin windows were just added in the bathrooms and kitchens where a solid firewall would be in a normal floorplan. Those thin windows are not designed to be the primary windows in the unit, but they were just added to let additional light in and break up what would normally be a blank wall.
You can see on the picture of 1280 west below, the corner units have the same floorplan as interior units, so there is this giant blank wall that appears on the corners of the building. It appears this building added small windows to that wall to add additional light and break up what would be a blank wall. They could have spent more money and made a dedicated floorplan for the corners, so both walls would have had large windows, but they chose a compromise and just added the small windows where they could in the existing floorplan.