Do an image search. By far the most common 3 fingers to hold up are the index, middle, and ring. But even that is not the point. He started with the most common, and then switched to the pinkie, ring, and middle. This is very uncommon, and that is exactly why it was mentioned. It's easy to hold up any 3 fingers, but hard to start with 2 up, like he did, and then switch.
Do an image search. By far the most common 3 fingers to hold up are the index, middle, and ring. But even that is not the point. He started with the most common, and then switched to the pinkie, ring, and middle. This is very uncommon, and that is exactly why it was mentioned. It's easy to hold up any 3 fingers, but hard to start with 2 up, like he did, and then switch.