The second floor is being re-plastered for a fortnight. Somebody sets a stop-sell so nothing on that floor can be booked, and everyone gets on with their week.
On the Thursday a regular phones and the desk sells them a second-floor twin. The stop-sell was applied where the property manages its channels, and the desk is not a channel — so the rule that was meant to protect six rooms protected them from everybody except the people most likely to sell them.
The guest arrives to a corridor full of dust sheets and a room that smells of plaster.
The distinction that prevents this is worth stating precisely. A restriction is a statement about the property — stop-sell, closed to arrival, minimum stay — and it binds every channel including your own desk. An allotment is a contract with a named agent, and it caps that agent and must never cap the house. Systems that treat both as "distribution settings" will get one of them wrong, and it is usually this one.
Why this matters to you: the cost is not one bad night. It is that after it happens once, your team stops trusting the stop-sell and starts keeping a separate list — which is the point at which the system has quietly stopped being the source of truth for anything.