Not necessarily favorable, but definitely helps! It means you get it. I didn't know what an athletic trainer was until residency. There's a lot of sports med docs out there with the initials MD/DO, ATC, LAT. My fellowship director was a student athletic trainer in college as well.
IMHO it helps quite a bit with relating to the AT staff during fellowship and beyond. It also helps when trying to get into shadowing positions during residency because there is usually a fellow AT in charge of scheduling. Also, the sideline experience helps relate to the athletes/families and also sideline etiquette which is a large part of how to gain respect/street cred with school/team admin.