I think your reasoning is correct and this is yet an another Airbnb calendar bug – see the one I just reported.
It’s shameful indeed that their faulty calendar leads to lost bookings and thus lost business both for Airbnb and hosts.
Welcome! We are a community of AirBnb hosts
This forum is dedicated to connecting hosts with other hosts. Sign up to get the latest updates and news just for AirBnb hosts! Note that we are not affiliated with Airbnb - we are just passionate hosts!