I'm not so sure about that. My grandmother, who certainly had not seen an iPad or iPhone in action before (she's 85, doesn't speak English and doesn't watch TV), figured it out within one minute of using my iPad for the first time yesterday.
If you think about the pinching movement, the distance between your thumb and index finger correlates to the size of the object. Increase that distance and the object grows in size (i.e. you zoom in). And vice versa. This is what I'd like to call "hyper-intuitive" and is the kind of thing people can figure out without being trained on it.
Same thing with double-tap to zoom. Not terribly intuitive, but that's not a big deal because there's a "hyper-intuitive" way to zoom. Double-tap becomes necessary only in very specific situations where only the hand holding the phone is free - which is not very common.
He just likes the app switcher better.
But he never would have discovered it if not for him coincidentally paying attention when I pulled it up once.
For example, I gave my mom a Microsoft Surface tablet I was lent for RT dev this weekend. It was in the classic desktop but I had a mapping webpage open in IE that responded to most touch gestures.
Because it was in the classic desktop, my mom was using her past experience and thinking of her finger as a mouse and hitting the little "+" icon to zoom in.
Not very "hyper-intuitive".