Why is cosine distance used in document_splitter.py

In the method score_paragraphs(in the class ShallowOpenWebRanker) the cosine distant metric is use.
Should it not be using the dot product metric, because the cosine metric does not take into account magnitude and tfidf is direction and magnitude?
From what I can see this would be similar to saying does the paragraph contain the word and not taking into account how many times the word occurs.