Nah, I don’t think they thought that hard about it. I feel the kid soldier trope is popular in Japanese media because you can put your characters in uniforms like it’s a school but they can also fight bad guys this way. Same reason why Type-0 went in that direction but there they actively deconstruct that and make it a War is Hell kind of thing. In here it’s honestly just a pretext, so I’m more inclined to say they just didn’t think this through