Driving Visualization Improvements first appeared in the release notes for 2019.40.50 (official thread and discussion thread).
Driving Visualization Improvements
The driving visualization can now display additional objects which include stop lights, stop signs and select road markings. The stop sign and stop light visualizations are not a substitute for an attentive driver and will not stop the car. To see these additional object in your driving visualization, tap Controls > Autopilot > Full Self-Driving Visualization Preview.