Obviously, I'm only talking about it logically. How does a player train to improve their jump shot and jump range shooting and not improve their FT shooting at the same time? They should be linked if for no other reason than they are linked.
Based on what empirical evidence? Can you name one great FT in the real world who has not spent hours practicing their free throw shooting?
The act of shooting a free throw is actually quite distinct from the act of shooting a jump shot.
That people who are good at one may also be good at the other is just as likely, if not more likely, to be a result of the fact that they have practiced both equally than your claim that the two are linked. Becoming a good FT shooter in BB already takes considerably less practice than it takes to become a good jump shooter.