This is my understanding of the rules at my airport. We allow pax in on a boarding pass dated for that day. Doesn't matter if my airport is the originating airport, or the destination, or not noted on the BP at all. Some flights will connect or layover in my airport but it is not listed on the BP anywhere. Don't care if they are "used" or not. Some people will fly in, collect their baggage and then come back thru security to eat.
Boarding pass dated same day doesn't necessarily help. The flight to the airport may have departed the previous day.
tht had just this issue last year when we did LHR-AKL via HKG. HKG not on the BP anywhere and the date on the BP was the date departed LHR, which is the day before departing HKG. Thus to clear security at HKG we needed a transit card as "proof" we were right to be flying HKG-AKL that day and not the prior day per the BP (as it appeared).
tht didn't pick up the transit card and thus got denied at security.