In the uploadforms the name of the input for fileupload (type="file") must be like "upload/path/$filename". MCRUploadServlet should take the submitted filename if the name in an other Syntax. So backwardcompatibility is provided.
If multiple fileselection is used, in the for multipart-fom-data the file are submitted under the same fieldname but other filename. MCRRequesParameter cant' handle this.