After posting the above, I found something relevant in my morning paper:

In the L.A. Times (picked up by Newsday, Josh Meyer considers the possibility that Khalid Mohammed was "playing to the jury" by framing his actions in terms that might create sympathy in American readers: "framing his life as an underdog militant."

"It is designed to have an American audience understand that there is another way of looking at the conflict between the West and radical Islam under bin Laden's leadership," said Jerrold Post, former chief personality profiler for the CIA.

Post described the "performance" by al-Qaida's former chief of operations as part psychological warfare and part artfully crafted argument.

"I take it as confirmation of the significance of his position, that despite his thuggish appearance, this is a very shrewd and rather precise individual," Post said.

Again, it's taken for granted that Mohammed said what's in the transcript, and did so freely. Nor does the article note that Post is also presenting a carefully crafted argument. [Note in particular the term "thuggish," as if honesty produces good looks, even in a man who's been in prison for years.]