[Adam]

Originally Posted by inigo montoya

During an endline throw-in following a made basket, a teammate of the thrower would be leaving the court for an authorized reason. A player in-bounding a ball is also out of bounds for an authorized reason. Therefore, no exception would be needed

I suppose the exception would need to be stated for the made-basket/end-line throw-in, for clarity. Not precisely an exception, but a clarification of "authorized reason."

A teammate out of bounds on a spot throw-in doesn't need a separate rule, because that's an unauthorized reason.

Authorized reasons typically include momentum. The rule for throwins simply indicates there is no such thing as an authorized reason during that time.