A customer need to extract from the audit the number of real reads of the content of the document, not when it was displayed in a list, or appeared in search results. They must know when the user actually displayed the content, either in preview, or in download. Viewing the content is entirely a different audit dimension as viewing the meta-data.
Even filtering System auditing when the documenlibrary browse page is opened in Share (not webpreview, but folder view), that for each child within, the audit configuration logs extra readContent entries. Is in fact the JSONConversionComponent that retrieves the mimetype and file size.
Here their configuration: