The iOS 10 APIs now spread out the work done during the lifecycle of a cell. Cells are now setup well before they need to be rendered, and the display process is spread out so a row of many cells doesn't need to be rendered at the exact same time right before they need to be shown on the screen. Cells are also kept for longer after they exit the screen, which means if the user quickly scrolls back the cell display method can simply be called again rather than having to get a new cell from the reuse queue, set it up, and draw it.
It honestly surprises me that Apple didn't make these changes sooner, because the impact on performance is dramatic. The iPhone 5s on iOS 10 has better scrolling performance than it ever has in the previous three years. This sort of thing is difficult to profile well even with XCode and Instruments, but I think it'll be immediately obvious to users that performance is improved, especially for users of older iOS devices that haven't had such a good time after being updated to iOS 8 and iOS 9.