I always thought it was weird that sometimes cars would just be missing or blown up when I enter the training grounds. But today I literally found a Bugatti lying around (I DONT EVEN HAVE THE SKIN??). Also the times of the training grounds are always different so I hypothesize it might be similar to a room that’s open for a certain amount of time where only one person can be in at at once but whatever they do to the map gets left behind (drive cars, destroy wheels, etc.)