Bill Nichols’ modes of documentary are highly problematic for one key reason. The vast majority of documentaries cannot be categorised under a single mode of documentary, a clear example being The War Game (Peter Watkins, 1965). This particular film can be argued to be classified under a number of modes – including both observational and participatory. Because of this, an uncertain middle ground is created and the modes are rendered useless.
The main reason for this is that filmmakers attempt to create a wholly unique and intriguing documentary, often with a particular artistic vision in mind. Because of this, documentarians often attempt to prevent their films from being categorised under a single, pre-conceived mode created by a single person.
Otis Morley’s A-Level Film Studies Blog 