Japonicus would be the assumption- however Burmanicus may also winter in the Korean peninsula (and does according to some literature) - presumably from Central China or Manchuria breeding populationsJaponicus is the expected buteo in Korea. Plenty of recent sightings in eBird, too.
I believe several of these have been redefined recently and that might be part of the problem.- it’s hard to find specific literature on the exact breeding and winter range of burmanicus perhaps because the taxonomy of east Asian buteos is complex and partly unresolved?
Yes, that’s actually ‘old’ news to some extent - treatment here
I believe that there has even been some reshuffling of subspecies after the original split.
The above is posted in a thread by Andy in the Taxonomy forum, and the authority making this change is IOC. That seems to indicate that there now will be consensus about using B. refectus for Himalayan Buzzard.Feb 12 Change scientific name of Himalayan Buzzard from Buteo burmanicus to B. refectus.