I like the approach but I think it's a big mistake to not strip stop words. He should focus on nouns and verbs imo. The top words he lists are all stopwords/grammatical particles "de", "que", "la", "y" etc. I don't think knowing those words will help to understand anything. I think if you understand only the grammatical particles in a sentence it won't help at all to understand the meaning of the sentence. On the other hand if you know the verbs and nouns but not the grammatical particles you can at least infer some meaning or what it's about.