I'm not justifying how Tesla's assistance works as I've driven a rental and it really is glorified cruise control right now.
That being said, I have a Honda with assistive braking and it is terrible. Shadows, pot holes, ghosts all seem to cause it to brake and not in predictable ways which is frustrating. I only leave it on, because I imagine one day I won't quite react fast enough to someone in front of me and it will save me the pain of rear ending someone.
But I definitely almost did when it slammed the brakes on a highway off ramp and got me rightfully honked at by the car behind me.
Whats worse is I'm not even sure if mine could receive updates at any point. Maybe at the dealership.