First, they only counted the nation’s 25 largest cities for which they had data. This means cities such as Honolulu and Oakland, both of which are much more transit-friendly than Portland, didn’t even get considered. In addition, “second cities” in urban areas, such as Arlington VA and Long Beach CA didn’t get considered even though they had the data and the cities are among the 25 largest in the United States.
Second, the transit score methodology is based solely on proximity to and frequency of transit routes. Whether those transit routes are actually useful is another story; some may be too slow or not reach many jobs in an urban area.