Look at the guys ahead of them. If you start Pannone and SRF in AAA they'll probably both be up by the end of April and pitch most of the year in the majors anyway. Why not take advantage of options to build as much depth as possible? Especially for someone like Reid-Foley, who will be 23 in 2019, or Pannone, who isn't going be a starter long-term anyway? Relying on mediocre young players to play full seasons in the majors as soon as they get their first taste of MLB action isn't how healthy orgs operate. Have depth everywhere. Let the young guys kick down the door before you relying on them sticking on the 25-man, unless you have a Vlad or Acuna on your hands.