You read that right.
Caesar's loves to push the Fuel Rewards Network (and in fact attaches the "Gas for a Year" Seven Stars experience to it), yet you can't use FRN at the Shell station located at the Rincon itself.
Pretty shameful.
Imagine someone gets that awful "Gas for a Year" thing, and in addition to the misleading (and poorly informed employees) nature of the whole thing, the person can't even get the free gas at the casino where they earned it.
FAIL