My update: I submitted the message to Airbnb at 4:55pm asking why my payout was a day late. I received the payout notification at 8:00pm and I can see the transaction is pending in my bank account. I still have not received a response from my message to Airbnb, but I did follow up and say that I have received the payout notification but am still wondering why it was delayed more than a day.
Edit: Airbnb tried to call me at 1:55pm today. The agent left a voicemail saying he would reply to my message. The reply simply said that the payout was released on Jan 6 and included a bunch of boilerplate stuff, but no explanation for why the payout was late. Not that I really expected one.