So, this visit, unbeknownst to the automated systems at Airbnb, has actually not happened yet. By the time California was back on Covid lockdown again, I was inside the 60-day no-refund window dictated by their policies, so I got in touch with Dan. He was extremely gracious and accommodating about coming up with a solution that would work for both of us, way above and beyond what any policy of Airbnb would require from him. What we worked out was beyond reasonable, and in fact generous, on his part.
I really look forward to a future stay at his beautiful place once it's again safe and legal for me to travel to San Francisco, and would recommend him as a host to anybody, anytime.