The study is not perfect. Kansas City's sole walkable urban area was the Country Club Plaza. One of New York's 22 is "Midtown Manhattan". Anyone who has ever been to Midtown Manhattan and the Plaza will not have any trouble discerning between the two. The author of the report says, in fact, that size and definition of a walkable urban area are parts of the report that should be better defined in future versions. There are other issues with the rather rudimentary way the cities are ranked. On the other hand, none of the other issues affect KC's standing for the worse (and may actually help).
The study concludes that walkable areas will likely increase nationwide in the near future, and that transit systems are an important indicator of the walkability potential of a metro area. With that in mind, the depressing part of the study goes thus:
Metropolitan areas that are not seriously committed to building rail transit systems—such as Cincinnati, Detroit, and Kansas City—may not have the option of walkable urban development due to slower economic growth and weak tax base. These slow growing metropolitan areas without rail transit today may be at a competitive disadvantage regarding future economic growth. This will especially be the case if crude oil prices continue to rise as they have since 2002 (increasing nearly three fold). These metropolitan areas may have “painted themselves into a corner”, due to both rising energy costs and the market opportunity of walkable urban development.