There's only one way, according to the printed rules ( quoting from on the reverse side of a preprinted EEO I received in the mail earlier this year) that they could wiggle out of it.

And even then it would have to have been invoked up front at the time you booked the stay:

"2. A limited number of rooms are available for this promotion. Certain blackout dates may apply."

I've used these things for years at a variety of FS Marriotts and Rens and I've never been denied the full use of an EEO by either a property or the Plat Reservations Line (other than what one CSR tried to pull that I cited in my earlier post which was reversed by another one in a later call).