IIRC, in 'The Corbomite Maneuver' his called was also different-looking from the rest. I think it was taller and had a zipper on the side.
Sulu's collar is the same, as is Baily's; higher with a visible zipper that ran through it. I chalk it up to still fine tuning the costumes since that was the first episode shot after the second pilot sold. The only one who had a proper fit shirt and collar in that episodes is Shatner. As the star, his uniforms had to be the best of the best since he was on camera the most.