I've stayed at this property 3-4 times in the past year and have to concur that they are not particularly great about Diamond upgrades. I have never been upgraded to their jr suite on the club floor, but have always been given access to the club lounge.
Typically, before they started closing grand wing floors for renovation, they'd put me in a nice jr suite on a regular floor. Once, I got a very spacious suite, but I think that was a fluke, as the room was due to be taken out of inventory for renovation right after my stay.
For my most recent stay last Dec, they claimed that all or most of the grand wing rooms are under renovation, and I was given an awful Terrace wing room. After talking to management upon check-in and the morning after, I was still stuck with the tiny room. I would not return until the grand wing renovation is complete.
If they are still so stingy and difficult with Diamond upgrades post renovation, that's not encouraging at all.