On top of all that, I checked out and (on a stay using certs + SNAs), the hotel billed me 150 AUD per night plus a credit card fee. Thankfully, I replied to the e-mail and they noted it was an error and refunded the charges without much of a fight. The refunded folio said something about Bonvoy, so it's possible that the hotel charged me what they're supposed to charge Bonvoy when an SNA gets used.