Re: Claymore by Yagi Norihiro
apparently half-awakened ones have a different level of control, and have gained a much higher level of that experience than most claymores.
I think it's still logical to say that they will lose control eventually, even if the 7 ghosts are displaying perfect control, because they have half-awakened and pulled themselves back, opening themselves to new possibilities that perhaps shouldn't have been open to them, either hidden by the organization or merely undiscovered. Like I said before, this false information may have been instigated by the organization as a means to control the claymore through fear.
We have seen that the 7 ghosts, and probably Teresa and a few others, who have learned to control their yoki more than expected, and they're deadly. This shows that a claymore is indeed capable of controlling herself. But if they were raised to believe they can't, they'll be inhibited by that and the fear alone will stop them from achieving more power, which is what the organization needs to keep them from doing what they want.