@William540
I experienced the same thing once when I was an Airbnb guest user in Japan - the guest sent me a similar message when I sent a message that we check-in okay. If anyone were to ask I should tell them I am a friend of XXXX (not host) in apt # XXXX (not the one we were staying at).
I completed my stay with no trouble, and when someone did stop me in the lobby to ask, I answered truthfully. I didn't see why I should have to lie or be inconvenienced because the host was running an ABB in secret, but I did flag the host after my stay.
As a host user, I've noticed ABB never refunds their own fees but always expects hosts to provide full refunds.