I don't know about it being a feature, but humans can definitely make the same mistake, and the follow-up here admittedly doesn't seem too egregious.

To me it's still a little "off" considering that your conversational partner just got called out for missing a detail that should change their entire reading of the riddle, but it's totally fair that you can imagine realistic human emotional states to explain it.

FWIW, when I tried the same thing with GPT-4o the model went off bizarrely speculating about misdirection about "the man" being the surgeon's son:

>Good catch—and yes, that's exactly where the misdirection comes in.

The riddle says:

    “A man and his cousin are in a car crash. The man dies, but the cousin is taken to the ER...”

    “I cannot operate on him. He’s my son.”

    The man who died is not the surgeon's son.

    The cousin who survived is the surgeon's son.