Exactly, officially. However, in practice (at least for elites) DL has been allowing SDC on the final domestic segment(s) of international itineraries.

Of course this doesn't help the OP, who will need to pay the $150 change fee and switch the ticket when award inventory is available.

Personally, I like the NRT SCs and would not be that unhappy about three hours connection time there, especially given that flights only operate once a day.