You're thinking about it all wrong if think it's about running full-blown desktop apps. This article gives some ideas about the productivity scenarios MS is trying to go after with this
Our early journey in crafting dual-screen experiences
medium.com
That article shows many serious practical problems with productivity.
Typing: It’s impossible to type with the thumb in portrait, because of the width and because you can‘t easily hold the other side without making the hinge rotate. On landscape, the width is too narrow to type with two hands. It seems like the least bad option is to type with the index finger.
When multitasking, I have to remember how applications are stacked up in each side. That’s something that happened with the first implementation of multitasking on the iPad. It’s even more difficult to solve when you have 2 physical displays. Also, I can’t resize apps.
It shows the action of moving an image from one screen to another as something pleasant, when you have to pass two edges and a hinge. Maybe it doesn’t seem like a big deal, but that’s a big flaw in the main purpose of the device.
I think I’m the target of this product. And maybe there are... 3 cases? where this is great. Maybe, for example, if I want to preview some photos that I want to attach to an email I’m writing, if the device is on a flat surface and I have it already open. But having to sacrifice answering to calls quickly, doing one-handed things comfortably, more battery, etc. for a few ideal scenarios doesn’t seem like a productivity boost.