I'm not sure that that is the logic behind it.

I was Plat for several years, most recently in 2004. However, I came off the road in 2003. What I was told by the SLC office was that a last-three-years-average formula is used, and that in cases like mine (where frequent stays suddenly became no stays at all), that status would be awarded based on my average stays over the previous three years. My downhill status slide did seem to work that way, except that I did end up with one additional year of Silver status that I couldn't account for.

Perhaps what's actually happening is some sort of hybrid of the last-three and soft landing methods, or perhaps Marriott applies whichever method is most beneficial to the member.