Thanks to all for the information. Looks like this weekend's stay is not going to qualify for Plat status. But at least we got the card in time to use it to pay for the stay and earn extra points that way.

Anecdotally, I called IHG Customer Service (Manila branch), and as always got someone who had no idea what I was talking about. She first told me I needed to contact Chase, then said "It's not showing Platinum because your account doesn't have the PC Visa listed as your preferred card." Oh, sure. I dutifully changed the info, but there is no way that's going to matter.