I'm also in this situation - have a 15 hour layover during a JFK-SYD flight next month. I've chatted PR via WhatsApp and they've said I will deplane, go through immi/customs, get bag, drop bags back to transfer desk, and then I'll be free to go and come back 10-ish hours later. Whether this proves to be true or not, who knows. If I mentally prepare myself for a 15 hour prison sentence at MNL then anything else will be a pleasant surprise.