  We prove a conjecture of Reiner, Tenner, and Yong which says that the initial
weak order intervals corresponding to certain vexillary permutations have the
coincidental down-degree expectations (CDE) property. Actually our theorem
applies more generally to certain "skew vexillary" permutations (a notion we
introduce), and shows that these posets are in fact "toggle CDE." As a
corollary we obtain a homomesy result for rowmotion acting on semidistributive
lattices in the sense of Barnard and of Thomas and Williams.
