It's not just uploads but any item that uses the email address as a unique user identifier (I'm not technical enough to explain this clearer but [1]).
An email address will be part of the xml in his uploads but also in his profile, which anyone can access by simply changing the url from https://archive.org/details/@foobar to https://archive.org/download/foobar. So, in essence, one just needs to have a registered account, independeltly any uploads made.