What he doing there?
It's what the game renders the stock buster shot as when you're Zero.
It seems, in X4 every resource for eithe X, Zero or UAX or Black Zero is loaded when you start the game.
It's not like X8 or X5 where both sets are loaded at once.
Edit: To clarify...
You cannot earn the UA in X4, it must be activated when you select X or Zero.
There is no way to get the UA to graphically show up unless you find some way to load the graphical data manually.
The UA is a whole peice and X either looks like he has it or he doesn't.
There are(is?) specific piece(s) of armor that when set will allow for the Nova Strike to be done or the UA to be visible.
Performing the Nova Strike while unarmored in UA game mode, results in an invisible dash.
Damage is dealt.
From what I can tell, if you don't set the UA when you begin a game, you can still use the Fourth Armor Nova Strike, but I am unsure of any other abilities the UA has so I can't tell if it's just missing the graphics or if it is completely locked out.
tl;dr He's investigating maverick activity in the Sky Lagoon.
PS: Flame, I uploaded a new version of the video.
PPS:
http://www.youtube.com/watch?v=q0xKFsrdIW4