Back before AA earnings were gutted, I had an AA Eagle flight not get credited. I emailed and got a similar reply saying that because the flight was “operated by Republic” I couldn’t get credit. It went back and forth several times with different people insisting that despite the flight being an AS codeshare and falling in the acceptable AA flight number range, it couldn’t be credited. I ended up calling and told the agent who laughed and credited the flight in about a minute.