Glad you had a good time.
Depending on when the rental was and how far before, if at all, that you made the reservation, it's likely you made the reservation/rental before the new policy went into effect and equally likely they grandfathered existing off-site reservations.
As others said, no longer allowed under the current set of rules.
In general IMO, golf carts are an expensive convenience but not a necessity at the Fort.
Bama Ed