Joseph Savage if we were to get technical, he could see the dog and he had a choice of what to pick judging by the dogs features (how dirty it is, if it was groomed recently etc.) whilst a coin is 100 % random and you just choose randomly
My guesses based on this video were more accurate... but I didnt go by the face. I went by the tail. If its up, female, down, male. Only half the photos even showed the tail so it was hard, but I was mostly correct. The females tend to have their tails up (revealing too much). Sometimes theyll also stand with their hind legs further apart (like that spotted one at 1:23 ), which is the opposite than is expected based on the external anatomy of that area, but more indicative of how they pee.