Why the Type 12 family began with conservative armament

Did Royal Navy conservatism explain the original weapon load of the Type 12 frigate family?

Yes; the ships were fitted for their contemporary requirements and had the ability to accept more later.

The question treats a roughly 4,000-ton frigate family as lightly armed for its size. The panel agrees that the Royal Navy designed the ships conservatively for the needs understood at the time. The hulls retained room to accept more equipment as missions and technology changed. Their initial fit should therefore be read as a procurement choice, not proof that the design lacked growth capacity. The short answer shows the difference between what a ship can carry and what a navy is prepared to buy at commissioning.