XHTML 2.0: Client side image maps dependent on the Image module?

http://www.w3.org/TR/xhtml2/mod-csImgMap.html says:
"The Client-side Image Map Module provides elements for client side 
image maps. It requires that the Image Module (or another module that 
supports the img element) be included."

Why would the Image Module need to be included when image maps on 
<object>s work fine? Is this an error?

/Jonas