I wonder what the distinction is between a “documentary” and a “non-fiction feature film”. I think Leighton was on to something in her post (that is Leighton’s blog, isn’t it?), but rather than trying to classify a film by what occurs in it and its style, perhaps we should examine purpose. How does Gates of Heaven differ from, for example, a documentary about whales? I could make the argument that the primary purpose of the documentary about whales is to educate its audience, but isn’t that also what Gates of Heaven is doing, in a way? But what about other traditional films? Some of them also educate viewers in the same way that Gates of Heaven does, but they’re not non-fictional.
Then I suppose you could get into the question of whether any ‘non-fiction’ film is truly non-fictional. Truth, in this case, is only what is presented to the audience and what is there is only what the directer wanted included. This doesn’t change between genres.
But back to the “non-fiction feature film” in question. I think I’m going to say that what makes it different from a documentary is both intent and subject matter. You could never make a traditional documentary about all of the themes that Gates of Heaven explores. (It would be a disorganized, incomprehensible mess.) But you can make a non-fictional film and accomplish this. If it doesn’t claim to be a documentary, audiences don’t compare it with their preconceived ideas of what a film of this type should be about, and therefore are more open to secondary messages within the film.