If I am reading this correctly, if I make a reservation at a sold out hotel and when I selected a "King" but it indicated it was noted, but not available...

Under those circumstances does the guarantee apply? Anyone have experience with it?

There are a couple of limitations. One is that Golds only get the guarantee for North American hotels not worldwide. (But you are a Plat so you don't have to worry about that limitation.) I'm also not sure that all International hotels have to abide by the guarantee. I think there are some exclusions for them.

Another limitation is that the hotel must have king beds to offer. I do believe that at least some if not most RIs don't seem to have king beds. So if that is the case, you should get their next largest bedsize (Queen for RIs I do believe.) There may also be some international hotels that may not have king beds.

But otherwise, my understanding is that you should be guaranteed a King bed. It might be worth a call to Reservations and ask them. Maybe there is some other exclusion that may allow them to not have to abide by the guarantee.

"As long as your preferences are noted on your reservation...."
However, I doubt the hotel is under any obligation to gaurantee you a king room if they alredy tell you it is not available when you make a reservation. Most of the time, they will do their best to accomodate your request.
All reservation confirmations spell out specific room type. Does your reservation say you have a reservaton of King room or not?

Nope...as long as it's noted in your reservation regardless of what you're told the gtd does apply

it is gauranteed if paltium

When u book online, sometime it won't allow you to specify 1 king bed, but you have to call to have 1 king bed gauranteed.
I did it many times while booking online and only can have 2 dbs available for booking, then called to have 1 king reserved

One other point that should be noted is that the guarantee does not apply to same-day reservations, or if you walk into a hotel without a reservation.