We should be able to exchange the Dark Spirit's Greed for the Offin Tett's Light Fragments just like we can exchange them for Kzarka, Nouver, Kutum, and Karanda's Latent Auras. You can already get all of the above mentioned boss auras from Resplendant Medal of Honor, however Offin fragments are the only ones you cannot get from Greeds. This feels like an oversight, as there is no reason for one item to have all auras as a reward and the other have all but one.