Because each stanza stops at the top using this attribute, The full poem is just not stuttery but provides a rhythm to it. It moves with pace and steadiness, but oscillates greatly. In reality this poem is sort of similar in composition ans model to 'Rime of the Ancient Mariner' https://andreslvzhj.therainblog.com/34380130/the-smart-trick-of-lovecraft-that-nobody-is-discussing