Well if you are talking about helping it by working it more Then the high bar will work the lower back more. it is higher on the leverage point and causes you to strain to keep that arch more . Like lifting a hammer from the end of the handle or near the head.
I see what you’re saying, but when I have the bar lower, I notice I lean forward more. Maybe to compensate for center of gravity, or just bad form.
So my back is not working as hard, leverage wise, but it’s going through a greater ROM.
Again, maybe it’s just my form (My pride likes to tell me that it’s the center of gravity issue;)