Isn't it just that if you're half a step away from 3 points, you might as well take the half a step back and try for 3 instead of 2 with a shot that's pretty much the same in difficulty?
He's (presumably) trying to maximize points per possession. His shooting percentage is a decreasing function with respect to distance from the basket. And there's a jump in the "shot made reward function" at the 3 point line.
Not following your logic...
A step backwards moves your balance and you have momentum backwards so getting an immediate upright jump shot without losing power/accuracy is more difficult.
Two different things at play here. At least this is my experience as a former competitive basketball player...