The Sterling unit should be attached to the wood studs.
After installation, there is a nailing flange that the wall board goes over, and is then taped and textured.
The installation depends on the 60" plus, dimension on the long side. It's a nice setup for adding a tub with walls.
Just install the tub and walls right out of the box, to the studs, and then add drywall up to the tub afterwards.