Hello, These are indeed wood boxes on cantilevered steel treads.
We recommend consulting with a structural engineer if you are
designing a similar staircase to ensure the supporting wall structure
will function as designed.

Owner could have signed a waiver or perhaps put up a temp rail in order to get the certificate of occupancy...then taken the rail down.

Hello,
Wood grades vary and these floors were chosen for their species and grain, the best thing to do is speak with your supplier about your desired grade and woodgrain. The material is 4" pecan/hickory for the floors (locally sourced in Austin) and the stair treads are laid up solid pecan.

They probably put up something passable for inspection & then took it down. The inspector isn't on the guest list of any ensuing cocktail parties...