A bolder take on the matter (one that is related to secondary bonding section) could be addressing the matter from a Bent's rule perspective: LEPs are better stabilized by s-type orbitals (or s character in hybrid orbitals). Linear polyiodine/polyiodide chains are widely pictured as combinations of 5p orbitals. Thus, in a sense, LEP sharing and chain bending increase the s-character in iodine bonding orbitals instead. "Shared" LEP is not much so. This is an alternative view on bond alternation.