That paper is amazing. Completely changed my view on programming. For those who find it a bit inaccessible (as I did on my first read), I wrote an article about it a while back, explaining it further and giving real-life examples:
That is a profound conclusion to reach. For the most part, I think it's true.
Without someone who wrote/fully understands source code, for example in abandoned software, the source code is a treasure map, the as-built plan of a building. It takes a lot of time and effort to orient yourself with things and make reasonable guesses as to what is going on. This aligns well with the original post.