Another view shows the shower floor pan framed in. Notice that the rest of the bathroom is gutted.
Some of the other homes in this area with the same floor plan had a master bathroom with a linen closet and 1 person shower stall in this space.
The fact that there was a bathtub here indicated that this bathroom has undergone some remodeling in the past. Or perhaps the builder just liked to mix things up
Framing shower floor