EDIT: DISREGARD THIS REPLY AND SEE ABOVE SOLUTION FOR PURGING CACHE
After inspecting the plugin code, I found the filter is ONLY firing for comment replies:
I believe this filter should be applied to base comments as well. After reading this documentation linked below I decided to edit the template and add support for the filter myself.
For anyone else following behind me, this documentation is a bit outdated as well because I could not locate the CSS file at '/wpdiscuz/assets/css/wpdiscuz.css', but thankfully I did not need it.
Now the author name I configured in the filtered function is displaying as desired. Again, I believe this should be included by default and I believe this is a bug.