abnormally close to your face after "strike." With the unbent pole close to your face it becomes far more difficult to position your "grip" properly than during the full application of "horizontal flexed pole rotation" where flexible poles "bow" smoothly to the side of the vaulter's "glide...
They "make the hill" steeper, turn up too fast, and stall out in gravity. If we go back to the lead arm it lies in a triangle with top arm, and the pole between the two hands. And its one of the few places/ways the vaulter can effect the placement of the CoM/potential energy ...
This appears to be confirmed by Figure 5.7, which shows Warmerdam in this phase of the vault and by Figure 5.8, (taken from Nicolai Ozolin's, "The pole vault"). Both mini sequences confirm that while the stiff pole vaulter did break at the hips to speed up the rotation of the body...