That was before the retirement of the LUS B767-200 fleet, and the reduction in group 3 lines of flying in both PHL, and more significantly in CLT. When the more senior pilots in those bases then bid over to the open Group 4 positions, and with the two winter seasonal drawdowns that have occurred since then to bump the junior folks off the bottom of the roster, your example of a April 2012 hire hasn't been able to reclaim the junior group 4 F/O position for some time now.

The OP was asking about the junior group IV FO DOH/domicile NOW not two years ago.