I booked the tour spontaneously only about an hour and half before it was meant to start. It was the only available tour for the day, and I was already guessing that something was odd and I might be the only person on the tour. The guide didn't show up, and I'm guessing he might not have seen the booking at all since I made it last minute. So, all good.
It wasn't a big deal for me, but I guess the booking policy should be improved to avoid this kind of unpleasant situation for either side.
I can't rate the guide nor his tour, the one star is for the "bug" in the system. Last minute bookings don't seem to work well.