Was repairing a house following a severe tornado a few years ago. Turns out the house was in a 100 year flood plain. As mandated by FEMA, any structure within that area had to conform to their standards when repaired. This included no basement allowed, if there were an existing basement they wanted the mechanicals moved upstairs, floor drains sealed, and the basement filled with gravel, thereby rendering it non usable. Construction of the new detached garage required flood vents in the foundation at ground level thereby allowing flood waters to pass thru the structure. Maybe what you have is someones interperetation of that rule.