Is that build location so important for cases like this one?
In the movie titles of those without assembly country I still see European titles, so having all these as Korean-built by default would be wrong too.
I think it is better not to have build info for 70% than having wrong info for 20% of them.

Indeed making a comment on each to change one by one would be time-consuming.
If you want to make a list of the vehicle IDs to be changed to one or the other, I can easily do the update based on that, and then change the rest to the other value.