for every <a> tag linking to a non-HTML files (pdf, mp3, etc), it happens to me that matomo fires the download tracking if I click on the link with the right mouse button, without actually downloading the file.
That is in fact intentional. A very long time ago, people noticed that right click β open in new tab (or download) was not tracked and as there is no way to detect those, it was decided to track all right clicks: