Could Ralph see the DME/GPS and altimeter clearly from the back? How sure was he that they weren't on an arrival and how can he be 100% without having clear sight of the instruments? Was the aircraft obviously in IMC during the circling approach or was the pilot able to maintain constant visual contact with the approach threshold throughout circling manoeuvre? How does Ralph know that the pilot did not choose to make a visual approach and let down into the circling area? How much experience has Ralph got flying at night?
The DGA is a quick and easy approach, unless you need to do a runway aligned to get low enough or if it was a murky black hole circling approach, why would a flighttime limited charter pilot bother going 10nm off track when a circle to land is far quicker?
Ralph could have had a chat and asked what sort of approach the pilot did to learn a bit without being too nosy. At the end of the day a PPL with no IFR experience and little night is not going to be up to speed let alone know where they are on an approach sitting in the back of a dark plane at night.