Had at least one unscheduled fuel stop at TPE for YVR-HKG as the CP DC10-30 couldn't make it n/s with any modicum of head wind in the mid '80s. Didn't record the date. No one permitted to leave the a/c at TPE, even if doors were open (FWIW that'd force a deplaning on immigration clearance if the tech stop was in the U.S.) so no pax taken on either. CP didn't serve TPE at the time.

Other time I may have taken advantage of an unscheduled fuel stop was flying GJT-xDEN on CO in the early '90s. IIRC, was scheduled to fly on the route by ATR but some weather event WX'd the ATR flight. There was a M80 sitting there and that's what I got put on to xDEN. Ended up having to O/N in xDEN due to the WX event.

Note: CX 888/889 originally started HKG-YVR-HKG in the earlier part of the 1980s (I first flew it in Dec. 1983 coming back in the new year). These RR-powered 747s (200B?) could make it non-stop to HKG most of the time but would occasionally have to make a tech stop in (usually) TPE especially during the winter. By the late '80s, CX888/889 ops was extended to SFO with 5th freedom rights, and then SFO switched for JFK by the late '90s. A/c was 747-400 by then, and went to 77W (and maybe 343 some days) by sometime in this century/millennium. Note that through pax were forced to deplane at YVR in one direction, and could either stay on the plane or get off at transit in the other. I believe this was eastbound and westbound respectively.

As for your HU flight hypothesis above, probably due to rights (if HU is even permitted to originate pax in SEA). Cargo, on the other hand........ May explain why SEA or LAX were chosen over ANC.