What would you call the type of work that his coach is prescribing?
You could definitely benefit from more strength work. I don’t necessarily think the prescribed workout is all that bad but I probably wouldn’t do it for 15 reps as by that point the quality will really degrade. 10 reps (and more likely 8) is usually my limit on activities like that.
a specific weightlifting endurance type of program. The intensity of the lift may make it worthwhile, but I think a better power endurance routine for the amount of time used would be one that is skipping, bounding, or running for 12-20s reps. For the session to be really working on power then either rate or weight lifted need to be controlled. I personally don’t really think power-endurance is effectively trained with weights beyond 5 or 6 reps for most types of athletes. If you are going to work power endurance beyond 8 reps then you have to start doing body weight type activities or medicine balls. For power endurance work to be effective I think the rate has to be near consistent throughout the duration of a set.