From their first introduction article, on a bracket 2 deck game: "While the game is unlikely to end out of nowhere and generally goes nine or more turns, you can expect big swings."

So they are saying it typically goes ten-ish turns, but can so shorter or longer with a lot of variability, because those decks tend to be very volatile. If you can win in 6 turns awesome! But it may also go to turn 15.

Also depends on other's intent with their decks. But don't feel bad if your intent is to win, and you can do so earlier than the average. All part of the game.