Not sure I understand the question, but I'll try. I don't seen anything of an issue with that box tube used as the slider/rail. For a unibody vehicle (XJ is most typical candidate) it WILL matter how that slider is attached. For a body on frame chassis, it matters how the runners are attached to the frame (welded or bolted) and amount of frame flex to compensate.
So are you asking if the capped box tube shown on the cherokee is good/bad for a body on frame chassis?