After a few quick rewatches, Jimmy didn’t have as much space between him and Horford as I previously thought.
A 3 on 3 in transition, Jimmy with the ball, Al backpedaling in a defensive stance, no help coming (Tatum’s sticking Strus after the previous play’s 3), plenty of time left, I would still expect him to try to beat Al off the dribble, initiate contact to provoke a foul call, and try to finish.
He did it over and over in the series to great success, it’s astonishing how he went with the pull-up.