What site staff know that a brief usually misses
They know which washroom runs out first, which entrance carries the traffic, which room is used far more than its size suggests, and what time of day the building looks worst. None of that appears on a floor plan and most of it never reaches a cleaning brief, because the person writing the brief is working from areas and frequencies rather than from experience of the building.
They also know what the current arrangement gets wrong. A short conversation with three or four people usually produces a consistent list, and consistency is the signal worth acting on. Where several people independently mention the same area, that is a scope problem rather than a matter of individual preference, and it belongs in the brief you issue and it is worth more than any single person's strongly held view.
