It's the same people but FSD was a rewrite of the system. The rewrite was to do image recognition and inference not from individual still images (pre-FSD) but

It's the same people but FSD was a rewrite of the system. The rewrite was to do image recognition and inference not from individual still images (pre-FSD) but from video feed from all cameras. This was enabled by the FSD chip Tesla started putting in cars about a year ago. Plus the improvements that come simply from gathering more data from cars and using it to improve the training of neural network. It's documented in Musk's tweets and Karpathy's talks.