It's hard to imagine that it's not a massive oversight to be able to end fights that have about six minutes worth of unique mechanics before they start repeating in less then a minute, but it's still technically not an exploit as you're not doing anything that was explicitly not supposed to happen like with the Ungarmax or UCoB glitches.

It's a little disappointing that there's basically no prestige value behind the duel titles now when any random joe with enough lost actions to burn can beat them, though.