BlackCat claimed responsibility for the hack. They also didn't expect Reddit to pay the ransom. Selling the data on the dark web is the most likely outcome. They want a payout after all.
I understand what you mean, but I believe Reddit themselves confirmed the breach. If Reddit didn't pay up, then the data has been/is being auctioned off on the dark web.
We haven't learned anything new since June. The BlackCat ransomware group claimed responsibility for the hack. They didn't expect Reddit to pay the ransom. So, like trifictional said, sold on the dark web is the most likely outcome. But there's no public indication that's happened yet. My best guess is they're waiting for Reddit's IPO to get closer to try and get a bigger payout for the data.
It was likely just a lie. Hacker groups often make claims they cannot backup, just for clout. If they had delivered on their promise we would have heard about it by now.