Aw thank you for the validation everyone. Indeed, I feel like with airbnb you need to remember that you're dealing with humans who have lives (though from what I understand that is less true over more true these days), and indeed those humans make mistakes sometimes. That is part of what you get when you're paying like 10-20% of what a hotel may cost you.
The place was relatively clean, it is a private room in a condo I live in. The guest bedroom bed had a pile of used sheets/towels on it from the previous guests, though everything else was relatively orderly (though orderly like one may expect when dropping into a tidy friend's place unannounced), a few dog toys on the floor, a dish in the sink, the pillows not artfully arranged.
I have found AirBnB to, sometimes, be very reasonable.. Other times, not so much. This seemed to be one of the times they were pretty reasonable. They asked me to snap a photo of the cleaned room.
They let me know the guests wanted a full refund, what did I think was fair. I said that refunding half the (nominal) cleaning fee was fair, as there were professional cleaners coming the next day of their 4 day stay. The airbnb rep let me know the guests had a change of heart and would stay afterall (tonight).
Though I'm going to emphasize that they please read the house manual, house rules, etc. I suspect they did not, as they had to message me on how to get in even though I have very clear instructions on entry that they clearly hadn't read.
Thank you again, everyone! I def't have a hard time navigating reasonable vs unreasonable guest expectations.
I, personally, try to be a pretty chill guest, and I generally don't hold my hosts to a higher standard than I would expect from the cheapest oldest motel/hotel that one finds like 45 minutes out of the city.
I did have a host in Chiang Mai who totally hadn't left the keys in the lock box, which could have gone really poorly if I wasn't a savvy traveler who had gotten a working local sim card.. And even that I look at as a hazard of using AirBnB.