The jam submission pages will show direct download buttons if you have files on your submission page that can be freely downloaded, the idea is to make people who are rating submissions having immediate access to your files without prompting them to donate. Those whoa are logged out will not have access to the direct download links though, and will instead be linked to your project page where they can go through the regular donation download flow.
Games that do not have downloads available (like browser games) will always link directly to the project’s page from the jam submission page.
Hope that helps