Just an update, after calling in I was told that this was bookable. I was put on hold several times as they told me that the second leg was waitlisted, but I mentioned that both legs were bookable separately online. I was then repeatedly given a warning about how I shouldn't book a ticket with a ~1 hour layover and should think about booking at least a 24 hour stopover. I explained that SQ12 uses the same plane and is sold as a married segment on both cash or miles and that for some reason it wasn't showing availability. I'm not sure what, if any, impact there will be booking this as a stopover. Would I need to have them see if they can convert this over to a married segment? I assume that I could ask my bags to be checked into the final destination, but would I have to check in after arriving in Tokyo? It's an odd situation, but it could be beneficial to others who are finding no award availability. I have no status and I'm planning on transferring in miles to top off my account for the purchase.