Opposite coloured bishops always draw
I agree. I should have pointed out it is probably not unique although the idea of using the bishop to stop the counterplay is probably essential. 3. ...a3 fails because of Bc1 and Bb2 defending c3.
The second move was the one that made it interesting to me. I can't be sure about uniqueness of the third move - at that stage the engine isn't entirely sure about the win, but I am pretty sure it is forced.
It is. The title was ironic. 
Many people will enter such endings and assume they have a draw. Playing carefully can get wins.
There is however a well known principle for winning endgames with bishops on different colored squares. Try to create 2 passed pawns with a decent distance between them. Black succeeds with his first move, white does not!
True. This one falls more into the category of superior king position - eventually forcing the opponent to sacrifice their bishop. But dealing with the counterplay is a key theme too.
Here is a game with this theme:
https://www.chessgames.com/perl/chessgame?gid=1004146
Here is another game