I've seen that before when I worked around steel mills. There just isn't room to store large equipment (like new ladles or furnace shells) indoors so it ends up in a storage yard outside. It's often made of 1" or even 2" thick steel, so the rust is cosmetic. From that, I'd guess that part of the production line (welding) got ahead and some steel shells were stored outside. When they're needed, they'll spend a couple hours in the sandblasting booth and be good as new. Sent from my moto g(7) play using Tapatalk
If not new, there is also a program in place where the tanks are sent out, stripped, refurbished and upgraded.
I believe the Anniston (AL) Army Depot is where all the Army's tanks and weapons carriers are refurbished and given new life. My first thought seeing NS 9330 in the top photo was that those bare hulls may have been headed to Anniston. The Depot has a large rail infrastructure accessible from the NS Atlanta/Birmingham main. The Depot is several miles long right next to the NS tracks, including all the assembly and storage areas. Furthermore, there are many historical tanks and weapons carriers stuffed and mounted facing the NS tracks presenting an awesome 2-3 miles long display from the train. It's awesome to see each time I pass on the Crescent.