around 3 years ago on PG BKK-LPQ, only 3 pax
couple of years ago QR DOH-RGN, only 4 pax on an A319/320 (and this was two flights consolodated onto one!) - told to sit where we wanted, the other three picked an economy row each, I pointed towards the business cabin, the stewardess nodded - happiness

- the other 3 stayed in Y ...