This is one of my biggest problems working in Illustrator on the Surface Pro 4. Adobe Illustrator does not rotate and allow you to work in portrait mode on the Surface Pro 4, but Photoshop does. It used to work perfectly on the Surface Pro 2, running an earlier version of Adobe Illustrator CC, but as you can see in the video, on the Surface Pro 4 running AI CC 2017 v 21.0.0, it does not work.
So why does Photoshop rotate and allow you to work in portrait mode, but Illustrator does not? Adobe knows about it, but no rotate for you!