True, but I wouldn’t overplay that argument. First, note that by excluding people up to age 25, most students are excluded from this ranking. That still leaves university faculty, researchers, and administrators, who no doubt bring up the average level of educational attainment. But there are many big universities, some bigger than Michigan, in towns of equivalent size or in some cases much smaller. A couple of additional factors come to mind.
First, the University of Michigan has a relatively low student-faculty ratio, which substantially ups the percentage of people holding Ph.D.s or other advanced degrees.
Second, Ann Arbor isn’t just a college town; it’s also a major tech and engineering hub. EPA has a major research facility in Ann Arbor, and Google and many other tech- and engineering-oriented employers have a major presence there as well. These companies primarily employ people with at least bachelor’s degrees, and many with masters or Ph.D.s. In its employment profile, Ann Arbor is more like Palo Alto/Silicon Valley than Columbus, Lincoln, Tuscaloosa, or other more “typical” college towns.