No, I'm not saying that. It all depends on the master. You'd want dither to prevent bit alignment errors in almost every situation. When you convert from higher bit depths to lower, you have to do soemthing to make sure there's no bit alignment errors from the conversion, and you want to make sure to remove excess headroom to make sure you don't lose data. If you have 80db of data, but leave 30db of headroom (reasonable when recording in 24bit), you need to move everything up, so you only leave 6db of headroom.