P-63 did ground attack missions and sank barges as well as any ships. After reading quite a bit into August storm, really the biggest problem is nothing is recorded. Damn straight the Japanese losing at this point are not going to document and the Russians never cared to write anything down anyway.
Problem is trying to account for something we have no clue what happened, maybe the Russians slaughtered the Japanese on the runway? Russia knows how that felt when the Luftwaffe did it, what did the Russians put in teh air that day? nothing? Virtually all the LAGG-1 fighters were wiped out on day one.
The Kwantung Army was pretty much stripped of any decent gear, tanks or aircrafts when the war started going bad for them in 1944, let alone July of 1945, and consider this - there was only ONE armored division of left over junk along with a 25-30 Infantry divisions of nothing but conscripts.
Yeah, conscripts facing the Russian red machine. Look at the Japanese Third Area Army for my only example, it only took three days to smash this field army into pieces, enough the unit took over 60% casualties. All his armor and most artillery was wiped out on day one.
So how do we know it wasn't P-63s doing that work? We can't claim it was entirely IL-2's that did that, however what we do know is the Japanese Third Army was in the area of operation of the P-63s.
Maybe if I can somehow manage to find information on this unit but a quick google check shows no books in japanese written by anyone in this outfit, then again who wants to write a book saying "WE lost the battle, and I didn't kill myself" something a Japanese won't do.