You have to read the NEC in context. You don't simply cherry pick words out of context.
This section is titled "More than one building or other structure" and 225.39 is titled "rating of disconnect" (in that other building) so it does not refer to the breaker in the main building (see "location" in 225.32) or the ampacity of the feeder, only the disconnect in the "other" building. They just want to insure that you can safely disconnect the "other" building, under load, at that building if you need to.
[This message has been edited by gfretwell (edited 04-07-2006).]