QR code check-in confirms presence by scanning a code at the desk, on the room door, or at reception. It proves the booking is actually in use, feeds accurate attendance and utilisation data, and needs no extra hardware beyond a printed code.
Because scanning takes two seconds at the place itself, it beats app-only check-in for honesty: you have to be standing there. It also powers auto-release, since an unscanned booking is a no-show the system can act on.