Maybe that is a way to balance fairly between primary and secondary weapon.
If your weapon is in any slot other than the first, it will have only HE or AP, and no sabot.
So for A/Cs, particularly 20mm Mod693, which is coax on the AMX30, you will want to keepp the same sabot ammo as if it was in the first slot.
Being coax is no reason for having degraded ammo!
