Is it normal for the RangeDeleter thread to continue working with the balancer stopped?

This is the expected behavior for the RangeDeleter thread.

By default, chunk cleanup is asynchronous to the chunk migration process. The balancer does not wait for the completion of the current migration’s delete phase before starting the next chunk migration. Chunks nominated for deletion are added to the RangeDeleter queue. The RangeDeleter thread continues working as long as there are items in its queue, regardless of whether the balancer is enabled or disabled.

If you want chunk deletion to block chunk migration, you can change the default behavior using the the _waitForDelete setting.

For more information, see Asynchronous Chunk Migration Cleanup.