I am requesting that since there are currently no known proven coaches or vaulting experts with demonstrable credentials yet, besides Inocencio and lavellenie themselves, that everyone be open to and respect the opinions of others.
Heres my theory of why Lavellenie is so efficient in his pole support phase.
From the very beginning of Plant and going into take-off and into swing I believe Lavellenie makes every effort possible to keep his COG as low as possible. That begins with a wider hand spacing to help keep his hips and torso back and low. I believe he has a very flat take off and basically just runs under the pole with a minimum of jumping effort or knee drive. This means he has no breaking effect from transitioning into a jump and therefore tremendous vertical velocity going into take off and therefor a great amount of force is immediately applied to the pole from his top hand. He just continues to drive himself under it allowing the force of his mass to be delivered to the pole from his top hand. With a slightly bent bottom elbow he makes sure the full force of his run up is delivered to the end of the lever (The top hand) and keeps it there throughout the entirety of his vault. Like I said he has no knee drive and in fact lowers his drive knee to match his swing foot while at the same time fully extends his left hand which together make his swing path and COG as low as possible. His bottom hand never goes over his head or has to be re-extended like Bubkas during vaulter/pole loading to lower it. His COG is immediately as low as possible and earlier on in his swing than Bubkas so he takes advantage of the gravity vector earlier illustrated by his immediate and more severe pole bend. Will points out the importance of the gravity vector in this statement and I believe it captures the essence of Lavellenies success:
It is therefore beneficial for the vaulter to try and have gravity compress the pole more and effect their swing less by braking the swing into the pole and present a better relation to gravity for as long as possible.
Lavellenie assist and maintains this perpendicular to gravity position by a wider hand spacing and a full extension of his bottom hand and the lowering of his drive knee to match his swing leg and by this time the vaulter/pole system is fully loaded with the COG immediately as low as possible. Much earlier in the swing than the PB method. I do not believe the swing is as long as Bubkas and I personally do not see any delay in it (I believe this would be a mistake). He simply goes from from a very low COG vaulter/Pole system loading swing path position to an immediate double leg swing (Frog like) into an immediate tucK (a ball) with both thighs and knees at each side of his hips while throughout the entire swing makes a concerted effort to maintain a leaned back position on the top hand for maximum pole bend.
From the moment the foot leaves the ground the flexible pole (for a right handed vaulter) immediately begins leaning to the left and bends to the left. This creates a larger window to swing through that the stiff pole did not nearly offer (Earlier stiff pole vaulters had to learn more how to swing around the pole). This left bend is sever but in Lavellenies case it is even more sever earlier on. This has a major effect on the physics of the vaulters swing path. As it is giving way left it causes the vaulters swing path to be oriented in that direction rather then perpendicular. To compensate for this, the wise vaulter steers their swing path to the right and up or toward the top hand. This is necessary in order to create a perpendicular swing. Altius, I have just answered for you why and how the sideways pole bend effects the Physics of the vault. Because Lavellenies pole bend is more sever and earlier on he compensates by orientating his swing path even more so to the right then Bubka's to the point his take off foot swings well more past the right side of the pole then Bubka's and I believe it is possible this counter side swing achieves better counter thrust bend to the pole at the top of his swing as well?
In addition Lavellenie has a double leg thrust into his extension, with more inertia generated by the use of both legs early on then Bubkas, from the pike position, which compensates for the inertia Bubka adds and Lavellenie misses through greater shoulder rotation at the top. As you know I have been a huge proponent of really emphasizing generating maximum energy at the top. I find it very interesting that it is while coming out of this Pike (I call the second body coil) that the vaulter is able to generate the most acceleration at any point in the swing and boy at what a great time going into fly!
Petrov: When the vaulter is unbending, the pole also has the highest speed of uncoiling
upwards, therefore, the combination of the pole's carrying capacity and the athlete's
unbending movement generates an accelerated thrust upwards, and by the end of the
unbending movement the centroidal axis reaches the maximum vertical speed
(Bubka's speed reached up to 6 m/s)
Of course Lavellenies also makes use of a top hand leaning pull as he tucks and a strong bottom hand push toward the pit (some call this a pull, but I prefer to call it a push, because the majority of the motion is away from the body) as the pole uncioils (The strong grippin action in this effort ensures the maxmum amount of kinetic enery is transferred to the vaulter and at the perfect moment) and a strong top hand push on the bearing point of the pole down to the box adds the final additional energy to flyaway.