In my opinion only, I think the Schindlers are grieving over a vase of cement mix. I just can't see Michael doing them any favors such as a proper burial. It was just to take the heat off of him for not letting them know, which got him negative publicity.
Michael Schaivo at the very least should have returned her body to them and allowed them to bury it in a Catholic Cemetery. He couldn't even return her ashes to them (this we know is true). And you are right, MS probably didn't even bury her ashes.