Thanks everyone for your replies. The guarantee referring to what has been booked makes sense now that I think about it. @:-)

Since yesterday the points redemptions have disappeared completely so currently we have no option but to stay put in the AC Hotels Bellevue.

We're staying next week but slightly concerned as it is a brand new hotel that has not yet opened. Also, I didn't realise we wouldn't get the breakfast benefit as a gold member until recently, hence the attempt to move. Hopefully a room redemption may reappear that we can grab.