It may or may not be worth fixing. Since tagging follows what we need in a practical sense though, it's not possible to tell whether it's important to fix until we actually have questions that show a need to be tagged with storyteller-system.
Historically we had few to no questions that were actually tagged with just storyteller-system; in practice it was (nearly?) always a redundant tag beside [cwod] or somesuch. My guess is that if we ever do have other games in the Storyteller system family, they'll only need game-name tags like aberrant and won't benefit from being collected together under a family-system tag.
If we have or get questions that would benefit from an independent storyteller-system tag though, or there is a clear and present need to encourage people to use the storyteller-system tag itself, we can always detach it from world-of-darkness and make that happen! It's just not really worth it for hypothetical uses, when the practical uses have (as far as I recall) always just been as a synonym for classic WoD anyway.