Not sure aboout Air. But I saw booking.com doing this. My check in is not till 4 p.m. And I received a message saying the guest's ETA before that time. It's ridiculous to not have something block it and prevent them from selecting an earlier check in. Just one more thing that will start the guest/host relationship off to a bad start.
Air just keeps pushing to put hosts in uncomfortable situations like free infants, free pets, and now this silly check in time.