The concept in the game is "You are the Commander in Chief" so all is enabled... You can order all organizations/configuration used during this epoch.
In the manual, maybe there is a confusion (sorry for that). Generally speaking, the French Army only used the mixed order (organization).. and it's the idea in the manual... but again you are the CinC.. all is possible!
So no real bug.. maybe a text without connection with the game.
Do you agree?
JMM
You are the game designer and I respect your design decisions, of course.
On the other hand, if only the French Army used historically the mixed order, as you say (I confess my total lack of knowledge), IMHO this should be reflected in the game, if, as I believed, one of your chief objectives is to reflect historical "reality".
I personally do not agree that everything should be made possible to me or to my (AI) opponent (for instance, I will never make a "super-hero" army in the OoB editor composed only of elite and guard units to beat the AI, although I can do it). If I played to win at all costs, that would make sense. That may make sense to the multiplayer community. But that is not I approach this game and I thought that this was also not the idea behind your game design.
Finally, if "everything is possible", I would like to be able to forbid the AI, if she is playing the allies, to use non-historical organizations. As I have no deep knowledge, but I use your game to learn (as I do with other games), I would also like that the game would direct me to what I could or could not do if I was a army commander in Napoleon's day.
Regards