You have implicit assumption that the person rewriting does nothing else. Understanding intention and solution is in there too for most people. A lot of calcul

You have implicit assumption that the person rewriting does nothing else. Understanding intention and solution is in there too for most people. A lot of calculus is rewriting blocks of solutions and applying them to problems. There is a huge chasm between how calculus and real analysis are taught. By your logic calculus should be of very low value. Yet somehow it opens a lot of doors for people to learn other things based on it.