Seems like they went to some effort to include some specific things like a certain number of people voting republican and them not being counted. Or the corporal ignoring his rebellion until it became big enough.
I have not seen the movie yet, but I can say two things. The first is that the movie is based on a very well-respected book by academic historian Victoria Bynum - if I had to guess, it might be the first book from UNC Press (the #1 publisher for works about early American military history) to be turned into a movie.
Secondly, the film has a website detailing what it took from history, as well as where and why they dramatized certain elements. Ideally, all of this becomes the norm for historical dramas.