Why did kuromorimine use a pz.II IN D.F 4?

So i just finished das finale 4, and i wanted to know why Kuromorimine uses a pz.II in the battle against st. Gloriana.

Like surely they has another pz.III at the very least, like why did they use an AA armed tank, against tanks?

For context i haven't rewatched since the release of D.F 3, so i dont remember if there were rules as to how powerful or balanced the array of vehicles could be. (But surely since they used a maus against ooarai there shouldnt be right?)

Anyway, feel free to discuss with (or bully) me in the comments ^{^}

p.s film was 3/10 needed more chobi screentime 😔 But for real i couldnt stop watching it, the animation was crisp as usual, defying physics like the rest of the series, and a blast to watch, 8.5/10