The Microsoft ones NOW have it there. He's talking about the pens for the pro 3. They had a button on the back and tell on the side. It's actually brilliant and I've kept mine even after getting a pro 17 and pro 4 keyboard. I can't imagine you write very often on your Pro if you prefer the back. Or maybe you never make much mistakes. But it's sooooooooo handy. The pen gets in the way of your view when trying to erase small little details if you use the back. And getting out of your writing position to flip the whole pen and erase seems, surprisingly, really jarring compared to writing and then adding pressure with your index finger and it's erased and release and you're writing again. Pencils need it on the back because there's no other option. I love it this way and on another account made a post about it that had a lot of upvotes. But to reach their own