Low passes aren’t flown any more by airliners. No necessity.
There is a gravity drop handle for the gear which allows the gear to fall by collapsing the up lock pin in the wheel wells and opening the hydraulics to return to prevent hydraulic lock keeping the bay doors closed. You can always tell when it’s been used as the gear bays doors don’t retract.
A simple hydraulic failure should still give you gear! I would suggest that the nose wheel was a separate issue. I would assume that they were circling in order to get the weight down. Why not dump fuel??? (I know the mini bus doesn’t have fuel jettison so I’m not sure about the A330, but being a LH jet with high fuel capacity I would assume it has the facility)
As to not declaring an emergency, IMHO that is awful. No nose gear IS an emergency and will not only affect the aircraft itself but also many aircraft inbound as well as those on the ground. That runway is going to be out of action for some time and giving a ‘heads up’ if nothing more is essential. Many carriers in the area seem to be very reticent at declaring emergencies.