As discussed in this thread, hotel can do whatever they want in terms of who will get suite upgrade regardless of SPG T&C. There is no transparency or consistency here. Therefore, it shouldn't be surprising that some hotels may put you at higher priority if you call in advance. I did not make this up myself. I had a chat with a rep at Sheraton Seattle last year. He told me that i had to call to get suite upgrade several days in advance. I was surprised when i heard this. He explained that by doing that they will know who really want/need the suite. Since then, on family vacation when i care about getting a suite, i will call in advance just to confirm that they know i want an upgrade at check in when available.

Again at Westin New Orleans, at one point the manager was telling me i would not get upgrade because I did not call in advance to let them know (despite I did). I don't know if she made this up as an excuse not to give me upgrade, or this is really how they do things.

I am just a 2nd year SPG plat. Still learning. So take this FWIW.