Except Zero does not have Soul body. what he gets, is his own variation in X5, Twin dream. Which leads one to assume that if you fight Zero, he uses Twin dream.
Also,to add onto Marshmallow, Those moves were also powered up. They all, with the exception of Double cyclone, act slightly, (in Soul body's case DRASTICALLY) different that their X4 versions. Frost Tower follows you around, and Soul Body, no longer creates a full clone of X, but shoots uncharged Soul bodies that are shaped like the Ultimate Armor. Actually, Its now more similar to Split Mushroom's own version.
So I assume that X also had that thought in mind. His weapons from X4 were still attached to the Ultimate Armor, and- wait, that makes me think of another thought. Ultimate armor was not Canon until X5 X vs Zero. in X5 it was also a secret. What if X found the Capsule and knew very well that using his old X4 weapons with it would soup them up? Though that also begs the question of why He did not use the Nova Strike. Though that can also be because of X being hesitant to go full force against his best friend.