Yes, indeed. Or... perhaps not for failure of effort on their part. Consider this. Might it be by design that they make declining a reservation request difficult, hard or impossible.
When this very issue happened earlier for me, inorder to protect my response rate the only way available to me was to infact "approve" the reservation. Airbnb isn't dumb. Their a very big business with lots resources. I'm sure they could fix this if they wanted to. So many resources infact that they are most certainly listening to this conversation as we type.