I have a 2 stays upcoming in Milan at SPG properties. The website was not able to work for me so I just called in. They applied them and looked for availability. Within 24 hours, the SNAs were deducted from my account and then I received emails they were going to start working on availability.
The app shows that the SNAs are not valid for my redemptions, however the CSR on the phone said they were applied.
One of my stays was booked Points + Cash Pre-Merger, the other one was booked Points post-merger.