We were already aware of American soldiers playing nose flute during the WWII. Indeed, one of the first Humanatone box was especially dedicated to the Boys.
Even the famous harmonicist Larry Adler had taken the opportunity of a radio broadcast to ask for sending harmonicas and nose flutes to the fighting forces (check this post).
I just found a simple testimony that these nose flutes were really played! Indeed, in the Fighting Squadron VF-9 history report, we can read that nose flute was played during free time
Fortunately, the file was declassified :)