What the PBS site actually says is:
which is not quite the same thing. Also the wiki article on that Japanese operation notes that number was a Chinese estimate, and that the operation had a secondary purpose of denying access to the area to the Allies for the building of airbases.
So without having a counter-cite, I’d say it’s very likely the Chinese estimate is unrealistically high, and what deaths there were, while doubtless large numbers, were not all due to the search for the Doolittle fliers per se.