Youtubers aside, "locked" means we could (theoretically) either have a dozen or so voices if most of the dialogue wasn't fully voice acted or the current four voices when every line needs to be voiced. In a game with so many dialogue lines, it's a massive amount of work to add even one more voice. So we're not getting a gruff dwarf voice, a hammy barbarian voice, a sneaky bastard voice, a pretentious wizard voice etc. We're stuck with the four we have now and I highly doubt we're going to get any more than that if everything needs to be fully voice acted.
But the problem is that you don't have ANY voices. You choose the protagonist and his/her voice and... your protagonist never speaks except for few places during the map exploration.
