Why twin mounts were harder for smaller naval guns

Why did twin mounts develop more slowly for six-inch and smaller naval guns than for large-caliber weapons?

Their designers had to combine faster handling with much tighter weight limits, making the mounting problem unusually demanding.

Smaller-caliber weapons were expected to sustain faster, more complex ammunition-handling cycles while fitting within a much stricter weight budget. Mountings for 8-, 12-, or 16-inch guns had a greater weight allowance. A physically smaller weapon does not automatically make a multi-gun mounting simpler to develop.