O.k., so you found a lower refundable rate than the refundable rate on Marriott.com but that rate was 'exactly' the same as the non-refundable rate on Marriott.com? Is this correct?
So in essence you got the lower rate and it is still refundable?

This is not how it is supposed to work, having the rate being exactly the same is suspicious and unusual. Marriott says you must book the lowest rate - they probably have a case if you didn't book the lowest rate, but I have personally never seen an issue w/ that