The link points to https://extensions.xwiki.org/?id=org.xwiki.platform:xwiki-platform-distribution-war:16.6.0:::/xwiki-commons-pom/xwiki-platform/xwiki-platform-distribution/xwiki-platform-distribution-war but this leads to the home page of exo, which is not correct. The script that executes and that is supposed to do the redirect is at https://extensions.xwiki.org/xwiki/bin/view/Main/?viewer=code
Note that the reason why the URL seems computed and strange is because we wanted to be generic so that it works for any flavor of XWiki. The code is generic and available at https://github.com/xwiki/xwiki-platform/blob/8ea02b48f840f0c0ec3174daa38b48ac638427aa/xwiki-platform-core/xwiki-platform-flamingo/xwiki-platform-flamingo-skin/xwiki-platform-flamingo-skin-resources/src/main/resources/flamingo/footer.vm#L32-L36