When somebody opens a document this is documented in the documents history.
The problem is that if you use the function "compress and retrieve" (download a bunch of files in a ZIP file) all affected files are also marked as "read" even if the user downloaded all documents of a project. Usually I any my colleagues are using this function to mirror certain parts of the document repository and then all files are marked read even if we did not opened a single document.

IMHO it would be much better to distinguish between opening/downloading a single file (mark as read) in difference to a large download of multiple files in a ZIP (mark it as archived).