It's not unreasonable for a guest to inquire about your cancellation policy, same as with travellers who book hotel rooms. Even though it appears on your listing, the guest may have overlooked it. You can chose which type of cancellation policy you want, when you create your listing: flexible, moderate, strict.
We've chosen "flexible" and have not regretted it. Guests are more comfortable booking if the policy is "flexible". We've only had one guest cancel, for medical reasons a month in advance. If someone asks, I just relay the description that is on the Airbnb website. You can do that too. No fear.