There are good reasons to do this on mobile: 1. Phones these days are tall. It can be difficult to reach the top of the screen. The height of the screen is gre

There are good reasons to do this on mobile: 1. Phones these days are tall. It can be difficult to reach the top of the screen. The height of the screen is great for reading content, but it makes sense to load the initial navigation pieces mid-screen. 2. The barrier introduced by scrolling is much reduced my mobile. It's trivial to flick your thumb up to raise the main content to takeover the full screen. The key is to ensure adequate information density after the initial scroll.