I definitely agree with Tim. Being a coach of high school and university vaulters, it is evident to me that many vaulters do not know the importance of the run and takeoff, and how they relate to the ultimate inversion and clearance.
A lot of coaches will still preach a stiff locked out bottom arm, pushing straight in front of the body, which just pushes the pole away and blocks a vaulter from inverting. As soon as a young vaulter lets off any of the pressure in the bottom arm, the pole recoils, thus losing all penetration.
I see way too many high school vaulters using this concept because they want to 'bend' the pole and get 'shot' in the sky. It is too dangerous and coaches need to teach proper mechanics.
The 'hip flip' as Tim calls it is a very common way of vaulting, in my opinion, for many young vaulters. They take off inside, with their hips underneath, A LOT, and block out their bottom arm to get into the pit. Then they let up on the arm to invert, and voila, pole speed gone !, or they keep the arm blocked out for the whole vault, and become the helicopter on Magnum P.I.
I agree with Tim when he says that focus needs to be on proper run and plant mechanics for beginners.