That does seem doubtful. Pirates has (supposedly) a capacity around 2,400 and the Haunted Mansion is around 2,800 (per
www.crooksinwdw.com, although I don't know how they derived those numbers). Mystic Manor (per Wikipedia, the source of all knowledge) has an hourly capacity of around 1,400 pph. Thus, I would have expected MMRR to be closer to Mystic than Haunted Mansion. Hopefully, it is at 2,000 pph or a little higher.