Hi Lizzie
That's a very valid point. Today for example, a lovely young couple stripped the bed, which we would not expect (they accidentally broke the zip too on the duvet cover as a result) but left their washing up for us to do. They meant to please us, but as they did their best, I wouldn't feel comfortable telling them afterwards that they had not got it quite right, as it would have spoiled the feel good factor on both sides. We'd shared our meal with them the night before so they were relaxed and happily going on their way.
Where host are not charging for cleaning, its expected that guests at least wash up their own cups etc, but I hadn't felt it necessary to spell this out in the past, as again it looks nit-picky putting that into the house "rules".
In the past we have a had a few guests say that our bathroom wasn't clean, simply because the 100 year old enamel on the cast iron bath's surface is pitted where a previous guest (not an Airbnb one, I hasten to add) used modern bathroom cleaner to clean it. Its a shade of green so we are unable to re-enamel it as we do the white bath downstairs. Others have disliked our Greek rag rugs in the hallway upstairs on an unvarnished wooden floor and said our floor or carpets were dirty, which was not true - so all down to expectations and personal stylistic preferences.
Its about matching the right kind of guests to the right home, as you (and we) are trying to do . One in the past complained that we are not like a B and B as we don't do breakfasts, but since it was a one-night booking for Chistmas day we did invite her to join our family meal at my daughter's house, but even then we didn't match up to her expectations.
Fortunately these are rare instances, but it only goes to reinforce what you are now trying to tackle, that a room on a person's home is a unique experience, not to be compared negatively with a commercial lodging place.