Well, no it's not the same concept. In MP the Space Jump is just a double-jump. One extra jump in midair is all she gets. In the 2D games, the Space Jump is a multi-jump, meaning she can basically hover in the air for an infinite amount of time.

In MP2, the Space Jump functions exactly the same way as in the first MP. It's just a double-jump. When Samus gains access to the Screw Attack, it pulls the camera out into a 3rd person perspective and allows her to multi-jump in a lateral direction only. She can't gain altitude when using the Screw Attack in MP2.

The multi-jump capability is now built into the Screw Attack, not the Space Jump.