My flight isn't until early October, so I've got time to see if things iron out. It was, indeed, a downgraded AC change. I was originally booked on a different regional jet that had first class, and my RPU cleared at booking, or maybe within 24 hours. Now, the downgraded AC and I have "X" fare bucket and 0% premium miles earned!

Was going to call this morning, early, but got busy and have decided to wait, for now.