Knowing the Tesla owner community quite well, I suspect Tesla was hoping nobody would find out it’s a dummy and complain that the newer cars are inferior to the older ones (like they did with the radar and ultrasonic sensors)
The best/worst example I've seen recently is the Jaguar V6 which is still inside a V8 engine block, so the company could use same mounting parts etc:
Seems clearly just an aesthetic move to keep symmetry and avoid retooling the large cover.
Also they can they easily move the cameras (center the remaining two) without partially retraining their machine learning?
1. Getting rid of features like passenger lumbar and justifying it by saying few people used it. I've also been around long enough to remember they temporarily got rid of side-dimming mirrors on Model 3, only to bring it back months later. Supply chain woes or whatever - it's better to be transparent about this.
2. Getting rid of features like ultrasonics and not having a production-ready hardware or software solution for things like Park Assist. When the move to vision-only Autopilot was made, there were also several limitations to the vision-stack.