One of the new additions to Windows 10 is how the OS handles tablets and desktops. In Windows 8, you were in either the modern environment or using the desktop, but with Windows 10, these two environments are blended together to create a seamless experience.
In the last official build of Windows 10, 9926, switching between desktop and tablet mode is a manual process. Even with the Pro 3, when you disconnect the keyboard, you have to tap on a notification to enable the 'tablet' mode. With later versions of Windows 10, such as leaked build 10036, you have the option to streamline this process.
As you can see from the image at the top of this post, you can now have Windows automatically switch modes when an event occurs, such as disconnecting the Type cover with the Pro 3. Or, if you never want tablet mode to engage, you can lock it to the desktop layout, or stick with the current setting where it prompts you to decide if you want to enter tablet mode.