It was Elon who said that, and it's a fallacy. For a simulation to be useful the agents in the simulation don't have to have a self-driving stack with computer vision, perception, elaborate driving policy etc.
What some people don't get is that this was primarily a sales event aiming to convince investors and the markets that Tesla is competitive in autonomous driving after numerous missed targets. That's why he (literally) trash talked things like Lidar and simulations where others currently lead ("they are doomed, doomed I tell you"
).
The thing is that capturing unexpected edge cases from a fleet doesn't just
happen either. Tesla can't and doesn't collect all telemetry form all cars at all times. They install triggers in a subset of the fleet that allow them to capture specific types of events. But this also means that you have to already know what you are looking for in most cases, which means you can probably also integrate it in a simulation in many variants.