This is the first I've read that "shot down" was part of the Japanese Capture theory, since that theory postulates that they were captured alive, held for a time and killed later. Surviving being shot down renders the theory even more unlikely than it already is. Japanese Capture is a seductive theory when one is not in possession of the facts -- as is Crashed and Sank.
Some of you may have read Robert Heinlein's theorizing on that same subject (pilot surviving being shot down) with reference to Gary Powers and his U-2. RAH thought there had been a forced landing due to mechanical failure, rather than the shoot-down the Soviets claimed (and the USA let stand as the acknowledged cause).
LTM,
Don