In a way, yes it is true. Irvine has very limited parking and almost always is overflowing. As far as I understand there are no official rules but you basically have to decide if you feel your car is cool enough to displace another car coming to the show. For example, I have a custom Miata, a couple beautiful Mercedes, and a pretty cool lifted truck that I will park in the spectators parking but I have a couple of cars such as a Chevy powered Mercedes, a Cobra, and some race cars that I will park in the show.
So as far as I understand it is discouraged to park cars that are not special in the show lot. Like if you have a Honda S2000 or a Mustang do you feel like your car is special enough to make it so a guy showing up in a Ferrari 275 GTB4 cannot park? That’s the way I look at it. cheers!