That's mostly, but not completely, accurate--at least, it doesn't hold up based on theoretical nonstop mileage from origin to destination. Using part of the very example you're working with, starting from SFO, SIN is farther than DPS. When ticketing SFO-SIN-DPS or SFO-xxx-SIN-DPS, SIN is a valid stopover point (and therefore not the destination) despite being farther from the origin than DPS. DPS could not be a stopover point with SIN as the destination since DPS is not a *A hub, despite being nearer to SFO.

Regardless, in the context of what savekenny is asking the general principle of not being able to choose what is your stopover and what is your destination is on target. I cannot imagine US pricing SFO-NRT-SIN (stop)-HKG at 90k (even though some people have reported stopovers in higher-priced zones being ticketed for lower redemption) for the simple reason that multiple *A carriers fly SFO-HKG nonstop--you're *very* unlikely to get an indirect three-segment itinerary with a stopover in a more expensive region instead. Don't forget the sixth bullet under "Partner Travel"--"US Airways is the final authority in choosing routing and the Dividend Miles partner to provide award travel, including the right to choose the most efficient routings and partners based on the desired origin and destination."