What survives the traffic and what does not
Some evidence of a proper clean persists regardless of how many people have used the room since. Limescale on a tap does not return in twelve hours. A dispenser filled to capacity does not empty to a third overnight unless the traffic is extraordinary. The underside of a seat, the back of a pan, the floor edge behind the door and the top of a cistern are all places traffic does not reach and a rushed clean does not either.
Other things tell you nothing. A bin with rubbish in it, marks on a mirror, water around a basin, a floor with footprints. All of those can appear within an hour of a perfect clean in a busy building. Judging a service on them produces constant low-grade complaint and no improvement, because the crew is being measured on something they cannot control. A fair standard measures what the crew controls and nothing else.
