I don't know what you mean by palm through. The palm always follows through. I was talking about four fingers down instead of index finger down (like watch kobe shoot. Kobe's index finger is really obvious. It even hits his thumb) or middle finger down (dirk) or ring finger or pinkie (nobody)
There are four finger down shooters but they're rare. Like steph curry shoot four fingers down.
Index finger is the form used by the best but people make the others work so I don't think it's a big deal
But even in the video you yourself posted DJ's feet are lined up at the line (Both left and right foot right on the line). His followthrough is to his left. See how squaring up his feet forces him to squish his left elbow into his body to line up his forearm with the rim? He doesn't do that consistently enough. It's a really awkward position to be in. A lot of times his elbow drifts a little to his left and makes his shot off center
I think you are thinking way too much about it. Some people just can't make them, plenty can't just switch up how their fingers work when they shoot especially those who has huge hands. You just proved that finger positioning or follow through don't matter because there are good and bad shooters on both end. Shooters just adapt better I guess and others don't, no matter how much they practice.
And some just can't change, it's simple as that. His form is still good though in my opinion and many other commentators believe so too included renown shooters and coaches. No offense but I'll take their word for it over yours.
How can you tell from that video that his feets lined up on the line? It's not an aerial view, no way to tell from the back angle they showed. You can see in pics he does stagger his feet though this could be inconsistent but I see his feet aren't lined up often.