Why the King George V class mixed quadruple and twin turrets

Why did the King George V class use two quadruple turrets and one twin instead of three triples?

The design began with three quadruple 14-inch turrets to preserve a twelve-gun broadside, but weight growth elsewhere forced one quadruple mounting to become a twin.

The 14-inch choice was intended to retain broadside weight through twelve barrels and a potentially higher rate of fire. As protection and other requirements consumed the available tonnage, replacing one quadruple turret with a twin preserved the design within its limits but created the class's distinctive mixed arrangement.