I'm diamond and never knew about the "top shelf" perk, would I be able to order an XO (as opposed to VS or VSOP) cognac?
XO has never been an issue at Bally's High Limit (in Atlantic City). I don't play at Caesars Entertainment Properties (in general) in Vegas; so I can't answer to that.
They go as high as Rémy XO, Hennessy Paradis and JW Blue (among other things) @ the Mansion Casino @ MGM (without additional approval), FWIW.