Hi @Adrian257 I do understand how you feel.... we had a very similar situation recently ourselves. The couple were a little older, say their mid twenties.... and we have a separate guest house attached to our home. When they arrived, they told us they may not be able to stay the night, due to 'work commitments'. They immediately closed the blinds as soon as they entered and left 5 hours later, quite late at night.
Although a little strange, this wouldn't have bothered us, but the bedlinen was truly disgusting after they left. I had to put on gloves and use all the tricks in the book to try and remove all the stains..... thankfully they did come out. And yet, not a thing had been touched in the rest of the room. They hadn't even showered!
I understand how your partner feels, and I also had trouble when it came to reviewing them, because technically they hadn't broken any house rules, but I really didn't like the dirty feeling of disrespect for someone else's property that they left behind..... we take pride in presenting a very clean, tidy and comfortable place for people to stay and enjoy. And, who did they think was going to clean up their mess!
In the end, I could only score them lower for cleanliness and an overall lower score.... but without going into specific details, in my comments let other hosts know that they hadn't actually stayed the night.
Since then, he has enquired about booking our place for a gift for some friends.... I told him that he can't book for a third party! I can just imagine all his mates lining up to do the same thing.... No Thanks!!