fop extension crop-box not supported for postscript rendering

When using the xmlns:fox="http://xmlgraphics.apache.org/fop/extensions" extension for fox:crop-box="media-box" fox:crop-offset="10mm", I found, that this extension works fine when generating pdf files. But it doesn't work for PostScript result files.
To prove this I have added a small windows batch script, which generates ps and pdf files for non croping and for croping fo files.
The resulting files can be compared by winmerge or so. Doing this you will see the different media/cropbox vraintes in the pdf files, but when comparing the postscriptfiles there is in fact no difference.
So the crop feature is not correctly implemented for the postscript renderer.

I have tested this with fop 1.0 and fop 1.1 rc1