Their concerns are seemingly exactly why we have invented hash functions. They have managed to keep BitTorrent (swarms certainly) free of bad actors even when there is considerable monetary interest in their existence.
Another one is to pretend that you have lots of chunks, and when someone challenges you to produce one, you quickly download it from another source and present it as if you had it all along. That's what the second paper prevents.
Can torrent clients properly handle being part of hundreds of thousands of item swarms at once?