Here is his video, he says they not only have an archive but also cryptographic proof that it was leaked via a Nostr event
nostr:nevent1qqsq0lh72qynk4ku0y8cl8t7suvmmdffmhma4l4zyjnggwjt5s8c90gpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsqsuamnwvaz7tmwdf6k6upwd4jsyg8ks058qd0h4485fc9e3na...