This is almost obviously untrue. This is a technique used for any task that requires thorough analysis of a space, like crime scenes and archaeological digs. Sometimes to a much more fine grained resolution than just quadrants. Saying that people can "just search the entire room" is like asking why can't you "just search the entire crime scene" or "just dig out the whole fossil". It trivializes the amount of effort needed to actually perform the task to the detail required, and dismisses the insight that a little bit of work division actually can improve performance for the exact same overall task despite the overhead it adds.