Eastham,
Our 2015 23RB has a corner shower and when entering the bath area to use the throne, we had a squeaky floor. I decided to figure out how to fix it today and was successful.
Turns out that the 3/4' square piece of wood under the shower door and behind the shower pan that secures the front of the pan to the floor is
stapled to the floor. The squeak is coming from the staples moving in and out of the top layer of the floor that is a sandwich construction consisting of a ~1/4" thick plywood sheet then foam below it. Certainly not thick enough to secure staples.
To fix the issue, I used three 1 1/2" long #7 pocket hole screws to secure the 3/4" square piece of wood to the floor at the base of the shower pan using a stubby #2 Robertson (square tip) screwdriver. Not the easiest task because of limited size of the access hole, but the pocket hole screws are relatively easy to start and drive without a pilot hole.
The result is absolutely no noise (at least from the floor, lol) when in the bathroom now.
The pocket hole screws are available at HD: