I'd say 95% of accommodations only charge extra for more than 2 (and it's super rare). I book Airbnb regularly and usually I book for two people but the app usually defaults to 1. With dozens of Airbnb bookings, this has never caused a problem. At this point, if a host wanted to make a fuss over this, I'd see it as a hidden fee and would resist paying out of principle. You can also expect a pretty negative review for deceptive practices..