I suspect this post will soon find its way to the Computer section...
To answer your question: The planes that you list are indeed the only flyable ones, but there are rumours of expansion packs either from Maddox themselves or from third party contributors. The 31 flyable aircraft types refer to different variants of the main aircraft - a bit of a cheat, but still correct.
The flight manuals for the other aircraft were probably used to ensure that the performance of computer controlled aircraft matched that of the real thing as closely as possible.