I don't have a centurion, just regular platinum card, but I stayed at Encore last week through FHR.
I called FHR to book 3 Encore tower suite rooms, but the system showed only 1 available tower suite room. The FHR rep called encore and they booked the extra 2 rooms. When I got to the Encore, the person at the reception desk said there were no available upgrades, and didn't bother to even look in the system (I think her name was Choona). I continued to press on about whether I could buy-up to the salon suite when another person at the desk overheard and said she would see whats available. She said there were 2 salon suites I could buy up to and there were 3 parlours available. When she said, that I asked for 2 parlours and a buy up to a salon suite. At that point the original person I was talking to had to give me the 2 parlours for free and charged me $200/night for the salon suite.
At the Wynncore its best to book a tower suite and then buy up to whatever else imho. Last time I was at Wynn I booked a tower suite, upgraded to executive and bought up to salon for $100/night.