It looks to me as if the author did a study based on a sampling population of one. His method of alternating positions was to slouch in his seat on a bike tour. He notes the hip angles; but is only interested in how it affects breathing, not muscle recruitment. Left unstated was that it also altered other measurements, such as his leg extension. So, even if we believe he was faster in one position, it's not valid to assume the difference in breathing was the cause. As theories go, however, I suppose it's no worse than blindly believing that closed hip positions climb better.