The Box Four shifter's main features aren't strikingly different from Box Three's. The key difference is its 8-speed platform. They've chosen to modernise the 8-speed in much the same way they did the 9-speed for Prime 9.
Just like the Prime 9, the Box Four shifters take advantage of the 'less is more' theme and exploit durability, simplicity, and reliability. 
Available as a multi-shift (pull several gears at once) or single-shift shifter (a sound choice for e-bikes).