[he continues standing for a moment once Erwin is seated, but then suddenly his leg twinges, and he elects to sit after all. He finds his eyes wandering to the wings on Erwin's back, as though trying to reconcile this addition to his image. His own are folded neatly against his back under his cloak and out of the way for the most part.]

According to Jean, it's the latter. Apparently he was brought here just before his death during the fighting in Trost.