In order for an athlete to reap the benefits of their training, they need to stress their body to a high degree. This stress must be specific to the goal they are training for.
Typically when you are working hard for a goal you will experience high levels of fatigue from the training stress. Their may be a performance drop off at some point during the training cycle, due to the high levels of fatigue. This doesn’t mean that your not improving it just means you need adequate rest for your body to realize the adaptations it has been making.
Once adequate rest takes place, you will realize the performance gains you made during the hard training in the previous phase.
Something I like to do during my athletes deload is have them perform unilateral work like above because there are many benefits they can gain decreasing intensity and recovering the previous heavy bilateral work like squats or deadlifts