It doesn't lock you into place in the sense of halting all sideways movement that is already in progress; it just locks you into place in the sense of not letting you request further movment. Powerslide works by just letting you keep sliding with your existing momentum, only amplified.
I've been strongly considering taking out powerslide anyhow, because it really adds nothing to the gameplay and is just one more thing for people to complain doesn't work properly.