Actually, 100%. Documentary - is a fiction, that imitates reality, and fantasy - is the reality that imitates fiction. Or, both of them is a reality, observed through the filter of author's mind.
But the next moment is important - visions on a TV-screen are shaped as much by the viewer as they were by the creators' teams. Those gladiators and fighting can be a true vision, so say, imitation of actual fights of the past, or can be allegory, each aspect symbolic of something else. It is the skill of the viewer to sort one from another.
The problem is, that every viewer has its own experience. And many of viewers create their own settings and expectation patterns. Say, Sci-fi means starships&blasters, fantasy means castles&dragons, western means cowboys&indians and so on...
If movie is marked as, say, Western, I hardly will be satisfied after watching a drama about LGBT-dragons seeking their happiness in interstellar battles and ancient libraries.
Same way, if I want to see, say, just sword fighting - I watch movies about Conan. From a "history movie" (not an "alternative history movie" or "fantasy movie") I expect at least minimal following historical reality as it is written in schoolbooks. If you name your movie " Gladiator", you must, at least, explain your customers what is the difference between "Gladiator fight" (which was a religious rite) and, say, entertainment in our modern understanding.
It's my personal opinion, I just explain my taste for books and movies.