The move isn't really that surprising - Jones actually got the start last week against Minnesota, but now he's listed as a starter. Jones has been playing a lot and Demetrius Dugar, who began the year as a starter, is hurt. Jones played as a starting CB through all spring ball before Evans' transfer became a thing, and started last year against Michigan State and Texas A&M. I think he's got game and he'll be starting in the future, whereas Evans is already more than halfway done with his Northwestern career, so all things considered its probably best to develop the sophomore Jones.
The left corner spot was a big issue in the first game when Ryan Nassib spent the entire side picking on Dugar with great success, but I haven't noticed a tendency of opposing QB's to do that of late - even with freshman Nick VanHoose really coming along at the other spot, breaking up three passes in the end zone last week.
VanHoose is the only cornerback to intercept a pass this year - two of NU's three picks have come off weird bounces or deflections. VanHoose also leads the team with six PBU's, as opposed to two for Evans, one for Jones, and none for Dugar.