The Freshness Feedback slider only affects the recommended lists for the day, not the XFAI plan.
For example, sliding 5pts to the left (more tired) will cause the listings to display easier workouts.
You could apply that procedure on days when gym work has you more tired/stressed than the Planner predicts.
If you want to insert weight training into your Planner to affect the gradient and Adapt Forecast to consider that stress in your plan, see this tread –