Why the R class was a precursor rather than a complete SSK

Why are the First World War R-class submarines not treated as the first true hunter-killer SSKs?

They anticipated the mission, but later SSKs combined submerged performance with guided anti-submarine torpedoes and more suitable sensors and weapons.

The R class embodied the submarine-hunting idea but lacked the guided anti-submarine weapons that made later SSKs practical. World War-era submarine-on-submarine attacks depended on extraordinary crew calculation, unguided torpedoes, and favorable circumstances. Later Guppy, Whisky, Romeo, and Oberon developments paired submerged performance with weapons and sensors better suited to the mission. The R class was a conceptual starting point rather than the mature form.