Wow. That I did not know. I'm also noticing that very short trips are pricey on UA as well. Did a weekend SFO-NRT and NH offered the best price back in October.
In that case, it's probably not worth going with UA for this trip. OZ can get me to NRT via ICN for about $1,000. Would still only get 70% miles, but the ICN-NRT legs can give a little extra and I hear OZ is a fine airline.