There's all these iconic photos of Walt Disney where he's pointing at stuff with a two finger point. I've heard that some within the company say that this is the example by which their resort employees always use the two finger point to direct guests.
In reality, he was holding a cigarette and the photos have been airbrushed. He died of lung cancer in 1966. Pointing with two fingers is just seen (kind of universally across cultures) as being non-accusatory. Like, say you saw someone talking to someone else and you cannot hear them (or it's in a language you don't understand); they're pointing with one finger in your direction, you may be inclined to think they're talking about you. If they're using the two finger point, you're less likely to think that... it's the same for airliner flight crew.
I'm a former cast member, can confirm. During Traditions (company culture and job orientation/training), they're taught to point with two fingers for exactly the reason you point out, and Walt Disney is shown pointing like that in the slides. They don't tell you, but most people eventually figure out, that there's a cigarette photoshopped out of his fingers.
I was in DAK Dinoland attractions for a while and then I worked in merchandise for a few years in the same park. A friend of mine was a monorail pilot around 2008 or so. Were you in the college program?
That's an interesting insight into human behavior that I never thought of.
I remember a long time ago, I was at Boston South Station with my then-girlfriend. We were looking at a monitor on the wall trying to spot when our train home would come in, and I pointed at it to show her.
A nearby homeless woman then informed me that it's unpolite to point. That always stuck with me. She was standing right in front of the screen...but now I know, I should've used two fingers.