My understanding on how upgrades are done, are that they are based on which direction you were originally booked for, especially if you are redeeming points for upgrades or using a certificate.

ie If your original room was for a Harbour View, your upgrade should be a RC room Harbour View. If your room was a Garden View, then your RC room would be the same view.

Only when the hotel upgrades you on their own due to oversold status and common PR relations matters, then you don't have a say as to where you face.

BUT be forewarned that the GRAND HYATT HKG are in the world of their own, and thus will impose their own set of rules.

One reason, why I'd only stay there if redeeming points.