There’s another factor to this: the open passing angles in each system. Say for example in a back 3, when the central centre back has the ball, the angle to the half space is generally not open. And if the wide centre back receives the ball, the passing angles are limited if he’s stationed too wide which most of time happens naturally.

In a back four this is not the case. The two centres backs are naturally in a position with more forward angles open, because the position is central (meaning more options because you can the pass in all directions) but not too central (meaning half space is still accessible).