Any night flying and the Night Visual Rating, should be done in a twin, with an instructor only and night circuits should be icus only.
Night flying, dual or solo, in a single is fine if you train and plan properly, know your limitations and practice.
Everyone is aware that night circuit training at a capital city airport,, shouldn't be done in a single,
as there's too much residential area around.
I'm not 'aware' of that. Maybe trucks and cars shouldn't drive down roads in residential areas either.
Night flying on dark nights away from extensive ground lighting needs a properly equipped aircraft, sound instrument skills and a good knowledge of sensory illusions and how to deal with them, it doesn't need a twin engine aircraft.