because its a continuation of jediknight, not the original dark forces.
jedi knight followed kyles transition from being a merc into being a jedi knight. by the time we get to outcast, there is not much connection with the old df plot. kyle is a jedi, and so, as it is a continuation of jediknight, and not kyle's passing into jedihood, its should rightfully be jediknight 2, not dark forces 3.
it may not seem right to you, as with many others, but LEC obviously thought it through for a while.
if you're losing sleep over a game name debate, you need a break from computers
take up something non jedi related, like footy