The inherent flaw in this type of comparative study, of course, is the idea that all the sports are ranked equally when it comes to viewing preference.
Personally, I am much more interested in baseball and hockey than I am in basketball and football. I don't care how "reasonable" a deal the T-Wolves are - I'd much rather see a Twins game.
Yeah, that's actually not a flaw, it's THE POINT of the exercise: to factor out the raw popularity differences between sports, like your Twins/Wolves example, and create a picture of how fans view a given sports franchise relative to the other ones in that sport.
No, the weakness of this interesting study (and thanks, OP, for posting it) is the relatively small data pool to draw on of fans with extensive knowledge of other franchises in a given sport. For example, how many baseball fans have been to a game in more than half the other stadiums in baseball?
Without sampling primarily fans with a strong knowledge basis for comparison in categories like "stadium experience", then the study is telling us more about how good a given franchise is at pleasing the fan base in such a category than it it's telling us how stadium experiences really compare by city.