Yeah, the comic wasn't always reliable in terms of uniforms anyway (the crew changes into their uniforms spontaneously between panels!) but the scene seems to have been shot with McCoy in his duty uniform. It does make more sense. If he's insane at this point, why change into different clothes when he's in the cabin?
I do want to see this scene, though. I have no doubt it was in the original preview. Along with the restructuring.