This is my understanding as well.As I understand it (again, IANAL), the 1,000 ft exclusion zone doesn't apply to those who are licensed by the state to carry a firearm. So, it really doesn't matter.
As to the sign at the door…. Are you sure OP that they weren’t written for instances where people were bringing guns in for service, trade-in, etc? It’s been a few years now but seems like I remember seeing a sign at a Gander Mtn one time that had verbiage to that effect. If you just glanced at it, it seemed to be saying “no guns allowed” but was really about making sure guns being brought for business purposes in were in a safe condition.