All it says is:

Free Room Upgrade: Club Level and Suites not included. Based on room availability at check-in and limited to a Member's personal guestroom.

You'd have to define availability. If a room is pre-blocked that might not make it available. One of the insiders would have to clarify what that actually means. I'd think that if you are pre-blocked (i.e. the day before or earlier, which I have) it would become a much bigger customer service issue than telling someone there is not a room available for them.

FWIW, I've spoke to a few GM's about how they handle UG's for PP's and most of them have said they should be taken care of up front and not left to the randomness of other P/G arrivals.

Last time I checked my reservations and cancellation penalties if I don't show up by 6pm, so other than people checking in between 3-6 the risk to the hotel on holding rooms is minimal. It would be interesting to know how many same day cancellations occur after 3pm, I'd guess they are less frequent than the number of PP's in the program.

Of course this debate all depends on your level in MR, Gold's want FC/FS, PP's want pre-blocked status based.

I'd suggest that if a PP calls the PP line and calls the hotel, the odds of the hotel giving away a pre-blocked room or using FC/FS to knock them out of a potential UG is going to be less than 10%, IMO.

That being said, I don't give a darn if the UG is the same room just with a view. My UG success is measured by how many suites I'm given, which is not covered by FC/FS as it is essentially an unpublished benefit.