It is not Yahoo's job to show only backlinks which do not have the nofollow tag for pagerank considerations. Pagerank is Google's baby and the Links section of the Google Sitemaps is something which will be more in line with the nofo'low links. Currently, Yahoo's SiteExplorer - https://siteexplorer.search.yahoo.com is the best tool to find out all the backlinks to your site. This is all most webmasters really want to know.