It’s not only the UI when it comes iPhone Duo. It’s the hardware as well. Currently it folds open to left and because of that’s it’s convenient for a right handed person. You hold the phone on your right hand and use the left to fold open.

To support a left handed person it should fold open to the right, also that way it’s a bit weird, although I’m curious to see how the animations would work for notes apps for Arabic language UIs where text is written from right to left.