VGFacts

As a huge Kingdom Hearts fan (if it's not already very obvious lol), I and several other fans noticed a neat attention to detail pertaining to Sora's battering weapon and item holding animation: It's actually an homage to the Valor Form drive form from Kingdom Hearts II (which is also the basis for one of his alt colors!). Long story short KHII Sora's outfit has magical powers that let him turn into different "drive forms" with one being Valor Form, which increases his Attack, Attack Speed, Jump Height, Walking/Running Speed, Air Combos and other things, at the sacrifice of kicking Goofy out of the party temporarily and having no access to Magic while the Form is active. The thing that's referenced in Smash Bros in his held item stance is Valor's ability to allow Sora to dual-wield two Keyblades at once with one weapon held across the front of him and the other across the back of his neck (when not attacking).

Here is a PKBeats video describing the Smash animation:
Can Sora Counter ANYTHING? -- Random Smash Ultimate Facts - YouTube
(Skip to 6:14)

Here is a video from a KH YouTube channel describing Valor Form in greater detail:
Drive Form Breakdown: Valor Form ~ Kingdom Hearts 2 Analysis - YouTube

EDIT: Here is more info on Valor Form: https://www.khwiki.com/Valor_Form

And yes, I did vote for Sora in the poll lol. I so happy he's in Smash.