Getting on the seniority list of a major airline can be delayed by multiple reasons. Luck with timing, willingness and ability to relocate, bonding arrangements, momentary perception of the benefits coming with a quicker upgrade in a non-seniority-based airline and many other factors can come into play. So, it's not granted that someone who rushed into flight training straight out of high school will necessarily be higher up the list than someone who has taken some time to learn something different before starting flying.