I think he made improvements with the long right cross vs Machida, and it hurt Lyoto, but generally yeah, he mostly arm punches. Or when he leaned in with rights against DC he pushed those punches. The uppercuts against Glover were much of the same. Doesn't turn with them and doesn't bend his knees, but him being able to land those shots is impressive.
Everything looks to be designed for speed to stay out of close range, but I don't think that's an excuse. Plenty of tall, lanky boxers with his body type throw hard. Maybe boxing is just the one area where he isn't super talented. Jones comes from a wrestling background and many wrestlers just have trouble losing shoulder stiffness when transitioning to punching.