A friend pursued the ledge south of Black Billy Head and spotted a possible exit up a 2-3m overhang to the plateau. He followed the ledge until it petered out beside an orphan rock, eyeing off a potential descent to the talus. He went back with a couple of friends and a harness and they confirmed that it does in fact go:
https://www.whatworkedforme.com/blog/po ... wneckPass/ I repeated the route with one of them a few days later.
Word of warning to the curious - this pass needs a little bit of work before it's maybe safe enough to do without a harness. I would classify it as tricky scrambling, bordlerline climbing, requiring coordination. The final down climb doesn't feel safe without a harness yet - though it may do with some auspiciously placed logs. I felt confident ascending it holding only a rope, but most would prefer a harness. Similar to the final Dog Face Gully climb. There are hand lines for the other steep section to the half way ledge, and one to hold as you walk around a ledge to reach it. Very steep, not for everyone. Also - the logs positioned against the overhang need a few more notches in them before they are adequate for anyone but the very tall and coordinated.
Nonetheless, I admire my friend's curious nature and I'm glad he was rewarded with a cracking new route! The ledge is stunning. Couple of exposed moments. Be careful, etc.