There are two different questions behind "can I sell this room tonight", and answering only the first is the most common source of oversell in small-property systems.
The first is room-shaped: is this room free? The second is pooled: can this room type be sold at all, given group blocks holding a count per night, channel allotment ceilings, stop-sell flags and minimum-stay rules?
A group block holds rooms by type and night without owning a room id or a reservation row, so no room-shaped check can see it. Vestibel routes every sale path through one pooled guard, and treats restrictions as property-wide while allotments stay channel-scoped — capping an OTA never caps your own front desk.