there is a small amount of download that is needed for overhead, but it should be extremely small, usually 1kB/s or less if tasks are stopped, but upload will continue when the tasks are stopped. If you can prepare some screenshots of unusual download speed with all tasks stopped, I’ll submt it to development, but I suggest as a test that you disable long-term seeding option and see if that stops it.
If DHT is enabled I guess the overhead could be more than 1KB/s. DHT can involve a bit of UDP traffic as long as your PC is an active DHT node with an open UDP port, since it may serve or forward DHT queries for other nodes even if your client is idle.
But 10KB/s shouldn’t be a real worry these days. In my view the benefits of DHT outweigh the small possible increase in traffic by a long shot.
If you don’t like it you can turn it off and go back to the stone age when trackers where the only means to get a torrent and the peers for it.
You won’t be bothered by DHT traffic anymore but won’t benefit from its advantages either.
You guys post some screenshots, to prove this. If it turns out to be true, we’ll forward them to the development team along with a report on the issue.