No one knows whether the soldier is a man or a woman or black or white or, indeed, whether there is even a soldier inside all that gauze and plaster casing.
On the one hand, they cannot simply send him home if it looks like a reward for refusing to fly more missions. The combination of force with specious and spurious legalistic justification is one of the book's primary motifs.
As he leaves the hospital, Yossarian evades another murder attempt. If he flew them he was crazy and didn't have to; but if he didn't want to he was sane and had to. Yossarian only has to make up a dream, before the psychiatrist is in deep discussions about what the dream means in his life.
By seeing the extreme, we realize how close our society is to that point. Heller employs themes in the manner of a musical composer, often introducing them briefly, then returning as the novel progresses, embellishing and augmenting as he goes.
He looks to many of the other characters in the book for help but only finds unsatisfactory answers.