I don't believe either of those books reference the internment camps. By 1944, there were a number of both Japanese and German prisoner of war camps in the U.S. In both the Captain Midnight and the Green Hornet books, the Japanese in the stories wear blue jumpsuits with PW(prisoner of war) written on the back.
As I'm sure you're aware, there was an internment camp at Tule Lake, but it was called the "Tule Lake Relocation Center". The "Tule Lake Camp" referenced on the road sign on the Green Hornet cover was 10 miles away from the internment camp. It was a maximum security facility that, among other uses, did house prisoners of war.