That was due to the ability he had gained after he reincarnated. The ability to control his body freely as he pleased. A combat technique requires extreme control likewise an Exercising technique.
But there was no body like David who could perfectly control his muscles, bones and body at such level that was why other would practice the technique repeatedly until they reached the Glimpse state, and with even more practice, they would advance to the next state, and when their bodies had gotten used to the movement and control, they could finally advance to the perfection state.
But David only needed to practice the technique a few time just to remember them and then, he would easily reach the perfection state with ground breaking speed.
He had perfected cyclone kick and apart from that, his physical strength was at a very terrifying state.