The "wrong" model is the intuitive, practical one. And all the padded, bordered blocks shoved into sized divs I've seen around the web tells me we're far from alone. The W3C oughta take note of the crapload of nonsemantic markup spawned by their unwieldy style dictum.
Be glad their original clipping foolishness never got traction. It worked like this: the default values for an unclipped region were 0,0,0,0. Clipping outward was done with negative values, inward positive. So, if you had a box that needed widening on the right and left, it looked like this -- clip:rect(0,-5px,0,-5px). This was actually implemented in early Netscape/Mozilla builds and caused a floodstorm of WHAT THE FUCK ARE YOU GUYS UP TO mail. The recommendation was changed in the next revision.
http://www.w3.org/TR/REC-CSS2/visufx.html#clippinghttp://www.w3.org/TR/CSS21/visufx.html#clipping