Sadly, there are a lot more images popping up on social media that are pretty obviously AI art + some manual editing (but not near enough to, say, give giants the proper number of toes, or have an archer actually have a hand that is holding a bow rather than some misshapen blob at the end of their arm and a curved line coming out of their wrist, etc.). Plus DDB has updated their blog post with artist credits, and two of the images in question are credited to someone who regularly creates AI art. The other images floating around aren't credited yet, but look very similar in style as those two.
So I'm no fan of Reddit either, but they caught this one, and it's not simply "someone didn't like their style and so said it was AI." People who are both for and against AI art overall are pointing out many of the tell-tale AI art artifacts that were common in late 2022 when these would likely have been created, and at least two images so far are outright credited to someone who says they use AI art.
It's AI art.
It's a shame and it's becoming yet another self-inflicted PR stumble for WotC, and I've lost count of how many that's been in the past year.