Hi there,
WP Offload Media Support Team here, Thanks for reaching out with your query we would be happy to assist!
I’m afraid that’s the expected behavior of the plugin. WP Offload Media can only offload files that have Media Library records in the database.
https://deliciousbrains.com/wp-offload-media/doc/developer-guide/#automatic-offload
However, our developers are already starting to support offloading files from the uploads directory even if they do not exist in the Media Library, which is the case for BuddyBoss files: https://deliciousbrains.com/wp-offload-media-2-6-released/#offloading-outside-media-library
Other files may be included in the offload process in the future, but we do not have an ETA for when it will be possible. For now, you may try exploring other existing WordPress plugins that can create Media Library records for files inside your uploads folder. We don’t have any recommendations on this though so if you’re going to test this out, we recommend doing so via a dev/staging environment first.
Please let us know if you have any other questions!