@Ralph102
re. 'We haven't had the occurance... I'll deal with that when it happens....'
I've hosted for 6 years - as a live-in host - and it's never happened!
The reasons are as follows:
1) I don't do Instant Book, so the prospective Guest is obliged to communicate even in sending a Reservation Request.
Indeed, I've never had an RR without some message, and no one has tried to pretend they'll turn up alone in my home. (It's not hard to imagine the reason: most would feel incredibly uncomfortable in trying to pull the wool over the eyes of someone they would like to stay with.)
2) It's not uncommon to receive Inquiry or Reservation Request for "1" with message re 'we' or 'us'. However, again I've never felt it's a deliberate ploy to deceive by someone who considers to stay in one's home.
Rather, the Inquiry is at a stage pre-booking.
Occasionally, I've felt it's an implicit signal for a discount on the additional guest charge.
3) There are easy ways to address the issue:
i) In House Rules state that only the precise number booked can enter the premises; though further assume that House Rules may not have been read, so the issue needs to be pointed out.
ii) State that Airbnb Host Guarantee pertains only to those part of the booking.
iii) Inform there is an extra charge for additional Guests.
The latter point usually reveals if the Booker has been implicitly asking for a Discount. If so, and I'm willing to grant it, I reply that I can do a 'Special Offer' via the website, when I can also formerly change the number of Guests.