I used to have this happen a lot. I don’t think it was a matter of a guest not telling the truth. I think mostly it’s an accidental error when completing the reservation. And sometimes it can be that when the guest sees your maximum guest occupancy, they assume they can invite that many people along later and it’s not a big deal.
It happened to me so often: I would get there and there would be dog hair everywhere for a reservation that did not include any pets (I accept pets but I would at least like to know if they’re bringing one so I can estimate my cleaning time afterwards), or I would have a reservation for 2 people and when I get there, there are 7 beds slept in and about 12 sets of towels used.
So what I started doing is, when I send the initial “Thanks for booking” message, I now include: “your reservation for ## guests and no pets is confirmed” This has helped on more than one occasion where a guest saw that and immediately noticed their error and messaged me back saying something along the lines of: “oops, we actually have ## people in our group and we are brining along our two dogs. I hope that’s ok”
That’s why I think in the past it was just an accidental oversight.
I also added a house rule that says “any guests or visitors beyond your reservation count needs to be pre approved”. This has stopped people from thinking it’s ok to just invite along other friends who decided they want to tag along on the trip or, if the reservation is for a local wedding or graduation, they don’t just invite the rest of the party back to my cabin to hang out.
Doing these two simple things has definitely helped in my case. Of course, you may still get the occasional guest who didn’t thoroughly read the message or didn’t read the rule about extra guests. In those cases I would personally just let it go and not mention it. It’s not worth the hassle of intervention from Airbnb, especially if it might just be a misunderstanding on the guest’s end. Sure, it’s not ideal, but these things happen.
Hope that helps you a little.