If I weren't an Airbnb host I probably would have assumed that no guests meant no guests overnight. Obviously, Airbnb's are not hotels, but that is the experience most people start with and many hotels don't have restrictions about bringing one or two guests to your room.
As a host, I do specify how many people can be in the house at any time and how many may stay overnight. At my property they aren't the same number. I didn't think about making that distinction until people started asking me about having local family over for game nights and cookouts.
Misunderstandings happen even when people think they are being perfectly clear.
Your host might have let your friend finish eating, but it is his house. When I hear about rules I don't understand, I always think there must an interesting story behind it.
Farm Diva