Room 12 checks out at 09:30. Your housekeeper finishes it at 10:55 and moves on. At 14:00 a guest arrives early and asks hopefully whether anything is ready. Reception looks at a list printed at eight in the morning and says no.
The guest sits in the lobby for an hour. The room sits empty upstairs. Both of them are waiting for information that already exists and has nowhere to go, because the only channel between housekeeping and reception is somebody walking downstairs.
The same gap runs the other way. A room reception believes is ready turns out to be mid-clean, and a guest is handed a key to a bathroom with towels on the floor. That one costs a review.
What closes it is not a radio. It is that room status and cleaning status are separate answers on one board both departments read — so a room is never ambiguously "dirty" when what you mean is "occupied and not yet serviced", and a housekeeper marking a stage complete updates reception's screen without a conversation.
Why this matters to you: early check-in is free revenue and free goodwill, and most properties cannot offer it reliably because they cannot see their own building. The cost of the gap is not the hour a guest waited — it is the every-single-day version of that hour, multiplied across a season.