Agreed, I highly doubt any Japanese solder would do this and based on the photo, it was probably recently captured and being shown off and not modified by an allied solder.
Not sure where this was taken, I could see Pilipino, Borneo, or southeast Asia fighters getting rid of extra weight.
I just noticed this was on the milsurp forum, the discussion I referenced was on gunboards. Since I mainly access forums on my cellphone Tapatalk app, I assumed this was gunboards.