One of the most valuable words in the English language -tough luck agapit! is WHY!! If we understand WHY certain things are important at various stages of the vault we will more readily understand the whole package.
So WHY do you need to "finish the take off" with a driving extension of the take off leg and ankle? The answer is so that we can put as much energy into the pole in the first stage AND also set up the trail leg in a position from which it can begin the whip of the body around the top hand in the second stage.
WHY is THIS important and why must it begin as soon as the drive is finished and the left leg well positioned? Because the athlete needs to be fully inverted BEFORE the pole begins to recoil to take full advantage of that recoil! That means the trail leg must move early - but only after the "take off is finished" - and FAST . This not only swing/whips it above the athletes head and moves them into inversion but puts energy into the pole at the same time -energy which also enables the athlete to position their com level with or even above the pole before it begins to recoil.
Athletes who do not execute these first two phases well,(WHY = Often because they take off under!!!) cannot put enough energy into to the system to 'stay long' through the swing/whip and are forced to shorten the axis of rotation by bending at the hips and knees and swinging up UNDER the bent pole, Not only are they now further from the space above the bar at that point than the Petrovites, but now they must shoot their feet for the bar without ever being able to put more energy into the pole in the third phase as Bubka did.
Iooking at this issue in more detail i suspect that Feonaova delays the forward whip swing of her trail leg too long after take off and this, along with a tendency ot slow her rotation by allowing both legs to extend, means that she is never in a position to fully exploit her great gymnastic ability in the third and fourth phases. If she could resolve this, she could be -at 5'3 and a little bit? the second woman to clear 5.00m!
Its what you learn after you know it all that counts. John Wooden