Terence Sumner Kirk of Burleson, a U.S. Marine in World War II, made the only photographs ever taken inside a Japanese POW camp.
A few years ago I was on vacation to Singapore. While there I visited an old sight of a Japanese prison camp and in a building at this sight they had copies of pictures that were taken by a prisoner at this prison. His also was with a homemade camera and it was a very elaborate system he had of putting the camera together, taking it apart and still being able to photograph the area. I'm not writing this to take anything away from Kirk but I do believe this would be another case and not the only case of photographs of a Japanese prison.
You are correct. There was a case of a POW taking pictures, apparently in the Philippines. In fact, some books including those pictures also include one of Kirk's. Look closely and you will see the shot of the sick POWs posing that Kirk took included in the Philippine photos. The fault is with the research for that book.
Kirk was the only one to take photos in a POW camp in Japan itself. It was much more difficult to do anything like this in Japan because there was no underground movement from which the POWs could get help as there was in the Philippines. Both men deserve recognition.