He ported the OpenGL 1.3 app to OpenGL ES by implementing the missing parts of the API that he needed inside the OPenGL ES API (albeit, as some people have pointed out, imperfectly).
That is not the same as rewriting an app to conform to the new API. There is, as you say, a HUGE difference.
That is not the same as rewriting an app to conform to the new API. There is, as you say, a HUGE difference.