Today, if you include a file download link into an email, you have to use Web Site Behavior (Download a File) to use as criteria. It is confusing because you sent an email and also perhaps you do not have an active landing page. So I think that the download a file must to be included into Email Behavior.

Also, will be great that its include (in both, I mean, Email Behavior and Web Site Behavior) that file download shows a dropdown menu populated with the file names incluided into a email or lading page. Today you must to write the name manually and the probability of make a mistake is greater than if you get a dropdown menu.