The angle that the shock mounts at has an impact on how effectively it can do its job. That’s pretty straight-forward physics. If the shock is mounted so that it moves in same arch as the spring, all of its effort is controlling the movement. If it is mounted at an extreme angle, such as these rear shocks on a flatfender, the control that the shock has is reduced. An angle of 45 degrees can require twice the amount of work by the shock to control the same amount of motion as a shock mounted straight up and down.