He put the treads on the stairs today. The wainscoting on the wall downstairs isn't painted yet (only primed) and needs another sanding from some final patching. There will be stained trim that goes under each tread that he hasn't installed yet. It hides imperfections and makes the tread look thicker. Everything for the stairway is painted or stained and ready for him to finish.
He had to wait to finish the wainscoting at the bottom of the stairs until he put the treads on, that is why the wainscoting isn't finished yet.
The upper part you see here is just dry fit. He hasn't glued and nailed it yet.