That is not necessarily evidence that the swiping animation is not pre-rendered. It just means that if it's pre-rendered, it can be slowed down, sped up and reversed based on the user's finger's motion.

I can tell you for certain that the OS swipe animations are not pre-rendered (you can easily tell, sometimes one or both of the views involved are animated for example), and I highly doubt anyone would do that. What would be the purpose? It's much more complex to handle, and there's no benefit.