luden's + ekko

not really sure if its a bug or not, but i noticed Ekko's passive procs luden's echo when other champs with similar passives (-cough- diana -cough-) dont. I know the item says that it procs specifically off "ability damage", as to if the pertains only to champion abilities or instances of ap damage, i would think the former. But in any case there's some inconsistency here.