As the subject says: AFAICT the Kafka project is the only project which publishes Javadocs as individual files on downloads.a.o.
What is the use case for this? The Javadocs are already published on the Kafka website. The mirror system relies on volunteers, and not all of them have lots of disk space, so it is important to minimise what is published. Additional files also increase the network traffic when synching (this is a minor consideration, but it's still a waste of resources if the files are unnecessary.) Sebb.