It basically came down to the PML committee approved the piece as it was written. Having certain instruments responsible for solos, etc. One of my questions was how is this any different from just rewriting an oboe solo for a trumpet or something? His explanation was that it had a bigger impact to the character of the piece. I didn't fully agree with the conversation, but he explained it well enough that I could sort of understand. It just modifies things way too much to be the same work that was approved. I guess think of it as you can't just take a trumpet quartet on the list and have your clarinets perform it without having it approved and added?
Again this is something if you're really curious about I recommend calling the state for a ruling. I would love to see this change just because of some works that have been added to those series that as a small school I will never have the instrumentation for otherwise.