There is no main long line. There are metal detector portals at little nodes along the way. Sometimes you realize it, sometime you don't.
When you are in the waiting area, sometimes these cute little petite uniformed female security guards come by with a wand and politely asks your permission to wand you and/or your luggage. Nobody ever says no.
They still catch their share of riff-raff which tries to smuggle drugs and, after convictions and appeals, treat them to a swinging time at the nearby Changi Prison.
Very interesting idea!