Right on, "shooting" alone is too broad of a term.
It is an unanswerable (is there such word?) question. Extrapolate from any field that requires standardized testing to practice/work in that field. It has been shown again and again that performance on standardized tests does not have a strong correlation with success in practical field. You can ace your test on paper, but be unable to apply your knowledge practically. You can shine in comfortable situation but collapse under time pressure. Etc, etc. When you choose your doc, lawyer, car mechanic, you don't look at their test scores, you look at their track record.
Same with shooting. The only true benchmark is that one has won all gunfights he's been in. Short of it, the best we can say is that better shooters would likely do better, but nobody can predict minimally required level. We don't know what's minimal level of proficiency is; technical proficiency could be a very small part of winning a fight; fight scenarios could be very different, with potentially drastically different demands.