IANAL, but my legal interpretation is you are at mercy of the property. "Enhanced Room Upgrades are subject to availability and are identified by each Participating Property." The property decides what to throw at you. Not just has the customer has no say in it, even more, according to your contract with Marriott there are no rules restricting the individual property in how they identify enhanced room upgrades that are available. The property defines it, that's it.

Over the years, I've read at least a 1000 posts where elites complained about not getting an upgrade to which they are entitled to. But I don't think anyone has wagered a court battle over it. For good measure, it's all BS.