Personally, I wouldn’t have considered that unethical. He may not have considered that she would want to stay the night so didn’t bring it up. Practicing polyamory and ethical non-monogomy and bring involved with partners that is one thing I have learned — specifically asking about boundaries is important. And taking the time to lay out my own boundaries ahead of time. If that happened to me I wouldn’t consider it unethical. I would just take it as an oversight on both parties parts. This kind of thing comes with experience and it sounds like Claire may have been new to the whole thing?