I doubt pinch to zoom falls in that category then. The vast majority of innovative (or unique) touch based interactions/gestures have to be learnt and cannot be intuited. As you know, intuition just means your brain recognizes a pattern.
I agree that it's hidden away but it's really easy to use once you know it's there.
That's hardly what I would consider a problem, since the app also supports pinch-to-zoom. The double-tap and slide method is purely additive.