It's not as different from the wiring issue as you suggest. In the case of the wiring issue, those that claim better wiring result in better sound honestly believe they hear a difference, just as those that buy the break-in idea do. They are hearing a difference that isn't present. A lot of both situations probably results from the same thing: they expect a difference. When you actually remove any knowledge of whether or not speakers have been broken in, or what wires are used, in both cases under scientific scrutiny, no one can perceive a difference.