Good question! I think someone was being a bad boy at one time. I believe they were reprimanded. Funny how 'Quality Assurance' seems to be lacking there in Bethel as they didn't catch these before they were printed and distributed.
But check out the latest pictures of Christ on the torture stake. The recent one I have is from the November 2008 Watchtower (the one about Hell with the orangey-red cover).
Riddle me this... how does this picture accurately portray Christ on the stake when the scriptures at John 20:25 and Matthew 27:37 are not represented in this painting?
I believe the WTS has some serious issues knowing and understanding the Bible as well as their lack of Quality Assurance.