If I understood it correctly (I didn't read the whole thing), the post is about how automatic change of variables is implemented in WL. On the other hand, the essay above is about how you can find a change of variables that transforms u''' + a u'' + b u' + c u = 0 into v''' + Z v = 0. It's about how exactly you can find such a transformation, not about how it can be done automatically in WL.