I disagree, Fims
From the Priority Club Terms and Conditions
Hotel Room Upgrades for Platinum Members: Platinum level members will be offered a complimentary upgrade, as determined by the hotel, which might include rooms on higher floors, corner rooms, newly renovated rooms, or rooms with preferred views. The upgrade will be offered at time of check-in, based on availability, and will only apply to the member's personal guest room. The hotel is not required to upgrade members to suites or specialty rooms. Upgrade benefit will not apply to rooms booked as a Reward Night reservation.
My point is that "as determined by the hotel" appears to be "as determined by whoever is on the front desk at the time".