Hey there! So if You listen to the intro video Joe says that the current program is evenly balanced, maybe has slightly less shoulder focus than others. So if delts are your weaks points and want to bring them up, I’d pick a program with more shoulders focus, like the come here cannonballs or Laszlo Kiraly’s program.
As for the exercise, substitues would be the lying cable laterals, the Y raise or the dumbbell lateral raise. If you watch the video on youtube (Terrence/Joe push day) when they “put it together”; they even say that the lying version was chenged to behind the back lateral.
But in every program, there is an icon in the upper right corner which well suggest alternative exercises for you.