I think common sense needs to be applied in situations like this
As an aircraft photographer myself I can see why people would want to take pics airside at airports so I have very rarely ever said anything to people at work I've seen taking pics in the terminal or the apron.
I regularly deal with football charter flights which get parked on remote. Try telling 300+ German football fans on a day out to watch their team play arguably one of the best teams in the world and probably the highlight of their year, that they cannot take photos while de-boarding / boarding the aircraft
On a few rare occasions I've had a few passengers who seem to think they are within their right to go wondering off the designed pax paths to get a 'nose on' shot of the aircraft, and even once try to sit their kid in the engine for a photo!
However, the airport I work at is
very spotter friendly so I see little point in stopping someone taking a pic of a plane surrounded by service vehicles, while being surrounded by a few hundred other pax when 2 miles across the apron you can walk above fence height only a few hundred yards from planes landing and taking off.