Yes, as I recall from reading previous posts, the properties choose which rooms they wish to offer for the SNA program and they do not need to be the same set available for upgrade at check in. So just because your SNA request gets rejected does not mean you won't get an upgrade at check in. And there's nothing to prevent things from changing one day to the next. Something as simple as a no-show/cancellation the night before you arrive can change everything. Any wonder people get confused/frustrated?