I see your point, but the Birthday Problem would apply differently.

It is the chance of “collision” between randomly picked elements two large enough sets of random data. If I understand correctly, the random data here would be “geographical fact” like bush density and road width. Set A is geoguessers’ geographical knowledge, and set B is pictures’ geographical features.

So if we picked hundreds of random picture and hundreds of geoguessers and asked them, the chance of one guessing one image is high. And the person would be largely dfferent every time.

In this case, we can give one specific geoguesser a large amount of pictures and that same geoguesser would get most of them right.