You've literally provided zero evidence (even anecdotal) to the contrary. Zero.
"No, he's not a bad finisher in traffic."
Right.
You know what, forget the word "finisher" if it bothers you. Let's just stick to the cold, hard facts. Sexton gets blocked a ton and he's making 33% of the shots he takes within 3 to 10 feet from the basket (i.e. floater range, where there's usually a defender or two between him and the rim). That's terrible. 9th best on this team.
In other words, Sexton is a very small guard who wants to score near the basket. The numbers say that it doesn't make much sense. Almost the whole freaking team is better than him in the 3 to 10 feet range, yet he keeps forcing this stuff.