Well you may be quite right in that observation. Tbh, he is most often compared to the very players you mentioned, each of whom is well known for their court vision. There may be a distinction without a difference here in me saying that Parker has never really had great court vision and you saying that while he is not as good as Manu, Boris, Nash or Paul, he does have "above average" vision, or better than his peers. I think it remains possible that he is 'above average for his peers' but 'not great'.
I think I mentioned in my original comment that no one else has court vision as good as Manu's. He is so far above everybody else (except maybe for Boris, but Boris so seldom plays the guard position I sort of take him out of the running on those comparisons) that TP is always going to look poorer in comparison.