Except he explains that it works like it does in the Messages app. If you're not familiar, the keyboard in Messages slides down/recedes when you start scrolling

Except he explains that it works like it does in the Messages app. If you're not familiar, the keyboard in Messages slides down/recedes when you start scrolling through past messages so that it's not in the way and you can see more content. Give it a try if you have an iOS device, it's a very useful interaction.