This is a very interesting thread and I might try it next time I am going through LAX.
I guess my question is... Does the Parking Spot not care that you jump on their bus to just go to In N Out?
I guess as others have said just tip the driver and it is all good?
I actually use the Parking Spot every week. They are IMO the best deal for LA area pax who need to park at the airport like me. The prices are very reasonable and they have so many shuttles you never have to wait long. The other thing...oh yes THE SPOT CLUB. Points for parking! I just redeemed 4 free days to run back to Boston and it was 100% free
Re; allowing you to hop the shuttle: I have never seen them say anything and in fact people who work at LAX openly use them to get back and fourth to I&O for lunch. The reality is they have so many shuttles that they are rarely full. But don't forget to slide a buck or two to your driver...they are actually really good.