In the video “Halo 4 Infinity Multiplayer” at 1:20 you can see the thruster pack in action. Here’s a loop of the video http://www.infinitelooper.com/?v=PsNWkjP65Cg&p=n#/79;80
What strikes me the most is that he is Not jumping in the air, but actualy evading forward. My theory is that depending how you’re moving the thruster pack acts differently. For example if you were sprinting you would do the lunge, but if you were just walking you would jump.