Suppport Gem "Devestate" in Leap Slam (and others) not inflicting armor break!

Put it in Leap Slam, jumped on enemies, it definetely heavy stunned them, they didnt get that armor break symbol under their name though so i assume this doesnt work? Kind of a big deal since thats literally the entire point of that gem? It works in my auto hit though and it also works in earth shatter, havent tried other skills.

EDIT: just tried with sunder too, also doesnt work with sunder! and it also only works with the spike part of eartshatter, not the explosion part.. i dont get this, arent these all hits?