When you're hanging suspended in your harness with your weight on the harness and leg pads you are defacto in a static position, not moving or in descent mode. When you're actively climbing up, either purely on the rope or with feet on the tree your weight is not on the belt or leg pads, or shouldn't be if you're climbing in an "athletic style". Typically a climber is sitting back on their harness when performing a fixed position work or recreational task. So it is important during those times when you're not actively climbing and sitting in your harness to have everything as comfortable as possible.
It might be that we are each talking about something completely different. But to give you an example, when I'm ascending I have no weight on my harness, it's all go until I stop, then I'm sitting in my harness. When I sit back on the harness leg pads need to be where I want them. For me that is more towards mid-thigh.
-AJ