I agree the wording of the email is a bit disconcerting, but undoubtedly true. They would have to be listed in the T&C though as it is not something they can pick and choose on a whim. So the scenario you describe would not work IMO.

Regarding Bulgari and other RC partner hotels, RC Reserves, RC Residences, RC Singapore hotel, etc. they have always been excluded from MR and RR since RC joined the rewards program. See # 11 in General section of the Marriott Rewards T&C for details.