Not to bash Jackson, who is obviously a very talented guy, but I get the sense two major factors weren’t put into this “rating”.
1. Number of penalties against, which Jackson has been notably bad at picking up. His aggressiveness, especially on deep passes, has cost the team a lot of penalty yards.
2. Gilmore’s special ability to Revis out a star receiver gives Jackson much more favorable matchups.
In all, glad Jackson and McCourty are getting some more recognition, as they are both really good coverage corners. To put them at 1-2 ahead of truly elite CBs, and especially ahead of Gilmore himself, makes this a laughable list. If Jackson and McCourty were both top 15, that would be incredibly impressive in itself...having them 1, 2, and 3 screams of unnecessary absurdity.