It looks to me like that graph was produced using k=3 for the k_edge_subgraphs() pruning step, and likely the suggestions for "octave" only included one or two

It looks to me like that graph was produced using k=3 for the k_edge_subgraphs() pruning step, and likely the suggestions for "octave" only included one or two other ML-related terms (because they are crowded out by musical terms). (For me the "octave vs" query gives "matlab", "Python", "pitch", "rhythm discord" and "key" as the first 5 suggestions).