Try arguing that with Airbnb if a guest claims they contracted Covid, because you offered the guest to clean themselves. I can guarantee you’d lose.
No, you offering the guest to check-in a day early if they do the cleaning isn’t “the policy”. Airbnb isn’t interested in your agreement with a guest if it contravenes their policies. And if you have signed the cleaning protocol and it appears on your listing, that is the only thing they will look at.
This may never happen, I’m just giving you the reality.