The claim is that they "took precautions not to 'seed' any downloaded files" - that probably means blocking all upload actions which is possible with many torrent clients. They may also have used a custom hacked client that didn't even connect to other nodes that didn't claim to have 100% already.

In any case it's really easy to configure a BitTorrent client to never seed. It would be dumb not to when torrenting for work.