RE: Why would you assume this?
The athlete has ended LP, and now is focusing their effort toward their primary sport. (I thought I read that somewhere in PP2ndEd; tailoring the intermediate stage depending on the athlete's goals?) They are still focusing on the primary lifts to continue the benefits of strength development using the most important exercises (i.e. the 5 lifts), but now are choosing additional exercises for the tailoring purpose.
Or should assistance exercises be seen not as a way to improve a specific performance goal (e.g. racquet swing power) but to improve the performance of the 5 lifts (which is the primary source of improving the racquet swing)?