Concentrating main guns forward can be especially weight-efficient under a treaty ceiling. One protected battery concentration reduces the length of armour and internal structure devoted to magazines and gun positions. An all-aft arrangement cannot simply reproduce the benefit because propeller shafts must run beneath the battery, complicating the machinery and protective layout. France would also have needed to develop triple turrets and accept an unconventional arrangement, so Duquesne retained a traditional four-turret layout despite its efficiency penalty.
Notable Point · 41:11-42:51
Why all-forward armament saves treaty displacement
An all-forward battery could concentrate protection and avoid routing propeller shafts beneath the guns, but France would have needed new turret arrangements to exploit it.