I'm scratching my head trying to figure out what the common thread is on the resorts that have the 3 confirmation restriction vs the ones that don't.
I have noticed there are no Westins, though you have one with just the Getaway restriction.
I even compared within specific geographic areas, and the only similarity I noticed, which I'm sure has zero actual impact on why, is that all of the Colorado resorts across Marriott/Sheration/Westin that don't have the restrictions are the ones that have air conditioning in the units, and all of the ones that don't have air conditioning do have the restriction. Within the Streamside complex, I Evergreen, which is not included, has in-room a/c but Birch and Douglas, which are, don't have in-room a/c. Sheraton's Mountain Vista and Lakeside Terrace, and Marriott's Mountain Valley Lodge are all included on the list and don't have in-room a/c. Sheraton Steamboat and Westin Riverfront have in-room a/c and are not on the list. Again, just a funny coincidence but not something that would actually account for inclusion or non-inclusion.
Maybe it's just something that MVW put out to the resorts to make on an individual basis?