Despite never recalling the extension, I know that I'm at least somewhat lucid in the moment, because if I need to change the end of a vault to make a bar, I do so. Kind of like tripping and catching yourself before you fall, it's a pretty automatic reaction for me.
The extension is one of the slowest parts of the vault, especially as you jump higher and higher. You already added most of the energy during the run, you did most of the steering during the swing, and now you have to hold things steady and get the pole to toss you in the right direction. Of course, that still takes a lot of physical exertion, but the motions are finer and more precise.