I think I understand the "non-difficulty" role of poetry as Jordan outlines. I wouldn't want to be a gatekeeper, oh no, not me! I recognize ptry-fr-its-wn-ske.
The formula which I was addressing, though, was "difficulty". If you are going to talk about this particular noun with respect to poetry, I think it has, as I said, less to do with technique than with ethics.
Jordan's "proxy" notion seems a little thrown, if you ask me. Almost a Horatian approach (its function is to succeed in expressing its audience's wishes & desires for it). I guess I'm more aware of the poet working to formulate his or her own dilemmas & puzzles ("out of the quarrel with ourselves..."). It becomes accessible, because both poet & reader recognize that our dilemmas are shared. & if someone is pleased/edified in the process - well, that's literary history in the making.