The allen screw does not push down on the pitman arm. It simply adjust the length of the pressure block spring mounted to the shaft by a retainer clip. This is the pressure block assembly and turning the allen CC shortens the spring, thereby increasing the blocks pressure.
If there is actual worm gear adjustment, that is taken out with the end play adjuster ring on the worm.
The end play is .01mm max , while the measure of the pressure block is a torque value measured at the steering wheel rotation.
Either will cause excess steering play, but one must check for worm end play before adjusting pressure block spring.
An easy way to check if the box is in need of adjustment [ instead of bad steering components] is to watch the pitman arm as someone moves the SW..
The utmost care should be observed when adjusting the pressure block as the Sw will not return to straight ahead position after a turn if it is mal-adjusted..