Webray is right. Sometimes they do and sometimes they don't. We had our PS #'s checked once at the Poly on July 4th for dinner ressies at Ohana. They weren't letting anyone into the parking area who wasn't staying there or didn't have a PS at one of the restaurants.
We have been there numerous times since (driving) and have never been asked. I think in the very busy times, they do check but even in not so busy times, I guess they could.
Lissa