I have always wondered about this since it states something to that effect on page five of American Passports.
it doesn’t matter
He is an enemy commander and is subject to being killed if located
He is no different than Admiral Yamamoto who was known to be flying in to Bougainville and shot down by P 38’s
The argument for not killing him was because there was fear about revealing sensitive info derived from code breaking. There was no problem at all with killing him.