Difficult issue for hosts and guests repeatedly, if prices are calculated per person.
We as a couple usually prefer a 2-bedroom-2-bathroom-condo on our vacation. During our stay we might have additional guests, so the occupancy will be four.
When I book the apartment, I always make sure to pay the maximum occupancy and have access to all the bedrooms and the whole space.
But for the rest of my vacation I want my privacy. No need to apologize or explanations what I'm gonna do with the bedrooms.
On the other hand, having an more bedroom apartment to rent, and without investigating to much in my guests privacy, I would always let two bedrooms open for two guests, because they might just be friends, maybe even looking separatly for "fun" during their stay.
My third or fourth bedroom instead would be closed as long as there was no further signs from guests travelling as three or four singles, wanting their own bedroom each of them.
So this would require further communication between host and guests before to make sure that everything is fine and there occurs no misunterstanding at least on arrival.
But a key for two is just a bad joke! There's no valuable excuse.