So you guys are all perfect swimmers in the arm pull department?
I guess 95% of swimmers are pushing water down form start of pull to arm at shoulder height.
Spearing deep is using the arm as a snow shovel pushing water up, but that force is less than pushing down force I guess.
Any water that is pushed down at the front is helping rotation, and bringing the elbow with the attached forearm/hand to the body after the wide point also has this effect a bit.
For me the driving force of rotation feels more like a four wheeldrive. The rotation can be helped at the rear with the kick/hip, with the arm thrown in at the front and with the underwaterpull, but the arm thrown forward movment is also originating from the kick.
If focus is on the kick, its hip first and shouders follow to extension, after extension it feels like shoulders lead, kick finishes.
If front and rear wheels work just as hard there is little twist between shoulders and hips and they rotate more or less at the same time, at the same rate.
All in all its hard to tell what leads and what follows.