The service centers are Tesla. It is one company. This is not a dealer going out on its own. Could be that a service manager made it up on his own, but why would he?
All of the components that are touched during the annual service on the S exist on the 3 too. How is Tesla going to say that they need to do their BS annual inspection on the S, but on the 3 its not needed? Not to mention that their service center numbers are going to look terrible if they don't have the massive profit from the annuals to offset the warranty costs.