I recently booked a room in stockholm that looked nice on booking.com. It was only after I booked that I was contacted by the owner and told how to meet up and get the key etc . I was pretty upset it wasn't an actual hotel but it was arguably too late to change things. It turned out to just be someone's apartment.
I have no idea if booking.com knew that. I do know I would not have booked if I had know for this particular trip.