The behavior of the sellers described in the article makes me think it's all but certain the songs are AI-generated. Imagine telling a jeweler a diamond looks fake, and they first pull out their handy diamond faking machine to show you how bad a fake diamond looks in comparison to what they're selling, then curse at you and close the store.
You can just tell looking at the article. $400 is a scam number for sure - too low for actual leaks (I assume news orgs etc would pay thousands), but enough that the grifter can walk away cashed up.