Last Poweramp exploits Android media (session/browser/etc.) API fully to support Android Audio + Assistant, and your headunit reads 3rd line from Queue, instead of MediaMetadata info (the current played track). Queue items have the layout as you described (3rd line is the “meta” info - same as in Poweramp lists).
This is a minor issue on headset side, as queue is an optional _list_, and the current playing track should be retrieved from MediaMetadata (where title/artist/album are separate fields and no “meta” exists). Nevertheless I think this can’t be worked around e.g. with some extra option.