Marriott does have a rule, though it may be unpublished. Resort fees are not supposed to earn MR points. (Of course, they sometimes do, but that's regarded as either an error or a failure to follow the rules.) I have personally debated this point with Marriott corporate folks. I posed the following question:

Consider two Marriott hotels in the same location. Marriott Hotel A charges $200/night for a room and has no resort fee. Marriott Hotel B charges $175/night for a comparable room and also charges a $25/night resort fee. The total charge is the same at either hotel, but a guest would earn more points at Hotel A. Does that make any sense? [Marriott says that the answer is yes.]

OK, what if Hotel B decided to reduce its room charge to zero and charge only a $200/night resort fee? What then? Would guests earn zero points at that hotel? [Marriott says that the second scenario would not be allowed by Marriott or by the local taxing authorities (because resort fees may escape hotel room taxes).]

Anyway, the whole thing is about as ridiculous as refusing to give Plats breakfast at "resorts," whether or not they have resort in their name!

Bruce