Extending your arm initially is premature movement and it's exactly why Sakura would be able to momentarily adjust her position to directly evade Air Palms specified direction.
Extending her arm wouldn't mean she would release the shock wave at the same time. She literally did this against the Juubi. Her arm was already extended,
then she released the shockwave, she didn't release the shock wave WHILE thrusting her arm. There's no reason for Hinata to be unable to, say, hold up her arm up like a sort of gun or cannon and take aim with Byakugan and shoot out Air Palm when she deems necessary.
Arm extended here
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Yet she fires Air Palm here
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Not to mention this happened.
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A straightforward flying kunai towards Sakura, yet failed to dodge. What about a straightforward shock wave that is invisible and faster?
I also would like to know why you think Sakura would even be able to react to such an attack when she has no feats of reacting to things from a close distance (5-10 m) that would allow her to dodge something as fast as Air Palm.
And the reaaib why Kisame didn't take a preconceived notion of Neji's attack os simply because he was combating (already to his disadvantage) Gai and Lee.
No, he landed after Lee blocked his attack on Gai, THEN Neji attacked: After Kisame landed and while Gai/Lee were still airborne. So he was combating no one when Neji struck.
Even IF Kisame was airborne when hit, and that's an if, the databook states he was blown away before even realizing he was hit, which shows the shear speed of the attack, regardless of whether Kisame was airborne or standing on the water.
But that's if Hinata gets the chance to muster the attack
And assuming Hinata does?
Sakura can destroy the ground beneath Hinata in seconds which will without a doubt strain the precision of the attack due to her having to adjust her equilibrium.
Until this is shown to be a legitimate threat to anyone, it's nothing but conjecture. Again, these people were fighting just fine on a ruined battle field. Sakura even punched the ground in Gaiden and it didn't phase Salad's balance at all. Sure, it was below what she did against Kakashi, but inversely, Salad is below Hinata, who was perfectly capable of balancing herself on a ruined battle field and executing 64 Palms. Not to mention, unlike Salad, Hinata would be able to put Chakra to her feet for better balance.