@Anonymous I could see why Airbnb might think this booking falls under the high risk category, due to the shorter notice of a week and being 'local', but it wasn't high risk. This guest had many 5 star reviews, not a new member, and was booking more than one night.
The thing is, all my perfectly legitimate bookings could be considered high risk due to the circumstances I described in my post. They are generally made within two weeks of stay, most are local due to the pandemic, and are often just a one night getaway out of the city.
The algorithm is catching more and more of my potential bookings in it's net. I've gotten around it well enough so far. This is the first time Airbnb has actually cancelled one. It's frustrating they can't see the forest for the trees.