P codes within shape definitions are used to synch both turrets during the cycle.
The P codes within the shape defined do not have to be sequential to the P codes with in the main program.
if you are pinch turning a roughing cycle this has the effect of making sure each cut is synchronised.
Finishing cycles, like you are using, (G87) will just synch each step of the profile.
Seems excessive at the start of the program to define and synch the start up of the spindle. Usually is enough to just startup from one turret then carry on after that.
It has been 30 years since I did any serious pinch turning and then it was with a Two turret Single chuck system. (LC20M OSP5000L-G)