No, it doesn’t. You’re still moving your center of mass against a force. That force can be gravity or the centripetal force applied by a curved portion of the ramp. A skateboarder that doesn’t change their CoM would be unable to perform any pumping maneuver.
And to repeat, you can still draw a force diagram and come up with an equivalent answer. As always, there are multiple ways to look at the problem. The force diagram may give the acceleration a clearer source, but where the energy comes from is less obvious.
I meant the COM bit where only dropping it down the ramp and raising it some time later, off the ramp, was the key.
What’s crucial is that there is an acceleration involved. That could just be gravity–but as the video helpfully notes, that’s a weaker effect than using a curved part of the ramp. Strong riders can apply greater force and get more oomph out of it. A strong, tall rider could get even more oomph, but given that they all only have a short duration to apply the force in, they’re probably more limited by strength.