I love the internet for little things like this. The author proposes a way to achieve the page turn-effect in the Square app, and the one of the actual Square devs sees it and responds directly to explain how it was _really_ done :-) The internet... connecting people for nearly 40 years.
Noticed that as well. Indeed, very cool!
It can be done different ways, it's neat to see the different approaches!
Square's implementation is so drop dead simple: page curl away a transparent view. I would've over complicated it like the author did with screen captures.