https://ia800105.us.archive.org/10/items/Military-Japanese/MilitaryJapanese.pdf Written by a legit Japanese person for use by our troops.
I tried to picture some of my swamp cajun relatives trying to speak Japanese. Good thing my heart is healthy. roflmao
Some Marine Scout-Snipers were taught some Japanese so that they may interrogate their prisoners. It all depends on when and where they were trained. Improvised schools probably did not include language instruction. Stateside schools had the time and opportunity and instructors. My speculation is that any Nisei in the Pacific were probably too busy working for intelligence to give language instruction.
Just sharing the target audience of the book. I like the GI Reader better. It's more my at reading level.