As for KJ, I'm looking pretty superficially at the situation. Who drastically improved his shot after 10K NBA minutes. I was not too concerned with what happened after or whatever else. Even the Jordan example had him shoot 38% in 89-90 and then fall back to his low/sub 30 %'s before getting respectable again in 92-93 at 35%.
Bottom line and what I think we are both saying: the odds of DD becoming a proficient 3pt shooter are slim to none and the chances he even becomes average are against his favour.