When I get a direct booking, I want to make sure that the dates are blocked on Airbnb, VRBO, etc.
I'd like quick access to the calendar synch option so no one can book instantly on other platforms. Yes, I've experienced a double booking on Airbnb.
With iCal alone (ie. what we calendar import/export) there's no way to force calendar systems to immediately sync unless the channel or other third party has a "Sync Now" button. Some, like Airbnb, do have that but they might still cache the iCal data for a few hours regardless.
I highly recommend looking at our API connections for Airbnb and Vrbo as they will guarantee immediate syncs and eliminate double bookings. Check out our support docs for more on that!