I usually agree with the host gripes on this forum...but not this one.
Airbnb was right to close this security loophole so guests' personal information is protected.
I've seen PLENTY of hosts who publish their calendar (with all details) on their direct booking site - open to the public/world. With a reservation confirmation number, guest name, and phone number, this is a big security risk. If that host also uses the "last 4-digits of phone" door code that so many of us do, that means anyone who knows about the insecure calendar knows how to enter the rental ANY TIME.
This was a failure on Airbnb's part to ever allow sensitive customer data to leave their site/control. Yes, it causes some bumps while we all figure new processes to share info with cleaners, etc, but it was a necessary and overdue fix.
IF YOU DON'T LIKE THE NEW iCAL, USE THE "TEAMS" FEATURE.
IF YOUR LOCK USES iCAL, talk to the manufacturer. You're not the only host with this problem, so they'll find a work around. Developers have until December to figure out a fix. It's not rocket science.