I would guess they're probably connecting onwards to Southeast Asia, because otherwise as you note it doesn't make any sense. It's an extra 2 hours to TPE vs HND from SFO, then conservatively assume 1 hour for a connection, then 3.5 hours to fly from TPE to Tokyo, but BR only offers flights to NRT from TPE so there's extra time to get into central Tokyo, totaling an extra 7-8 hours of transit time. But that extra plane meal tho...