I've found third-party sites (a) often only list one type of room (or at least a small subset of the rooms the hotel itself lists), and (b) often phrase the description of the room differently than the hotel itself does. And yet that doesn't stop the LNFs from being approved if all else is ok. So I would not worry about these things in and of themselves. If the rate (at Marriott.com, the one you actually have to book) is refundable, why not request, see if to goes through, and if you don't like the result, cancel the reservation. What's lost except a few minutes of your time? (Well, up to 24 hours of your time if you'll not be able to do anything else until you see how LNF responds! )

In cases where there's any possible confusion about how things match up between the Marriott site and the third party site, I "guide" the LNF folks with comments, maybe like "room type is the same in both places, but phrased differently on each site".