@Mary-Grace8
We get this a lot. Usually catch it in the pre booking vetting process, but not always.
In my experience, it's rarely seems dubiously intentional. They just choose the lowest cost option and book it without reading anything.
In other cases, they've booked it for x-pax, and later somebody decides to join them. No thought is given to how that may impact their booking.
In these cases, the guests have no problem paying for the extra persons as soon as they've been informed. All good. Everybody happy.
Except the couch. We wouldn't allow that either. And if you don't have enough beds, then it's not your problem, it's theirs. You'll have to book something else. Sorry.
There are a few cases where it's intentional, and we know this because they make excuses that sound fishy. For example, "I'm booking this for my parents. I'll be staying elsewhere, but I will be around if you need me". or "I'll be having a few friends over, but they won't be staying". They know from the start that more persons cost more money, they're just trying to get it cheaper. But you can sense it if you're a bit perceptive. Better to confront them straight away. (We lock unbooked bedrooms, and no, you can't use the sofa).
But then, it does beg the question of whether you're attracting the right type of guests. Are you under priced? Cheapness attracts cheapness. Let others host those types. Price a bit higher than everybody else. When they're booked up, you'll be the only game in town. Besides, You have enough to worry about.
It's all part of hosting. Stay aware, figure out where your pricing should be, and learn how to diplomatically deal with "special" guests, and you'll do just fine.
And don't depend on Airbnb to have your back. It's just a booking platform. Use it for what it's good at. Everything else is on you. Go forward with that view, and you'll have fewer problems.
Good luck.