I believe GP misspoke or misremembered and is referring to GDI, not drivers. GDI is the original Windows 2d graphics interface, widely used for drawing UI.

For performance reasons it lived in the NT kernel, together with the Window manager (which also draws windows using GDI).

Vista moved to a compositing window manager, I believe that was the point when GDI moved fully into userspace, drawing into the new per-window texture buffer instead of directly to the screen. And of course Windows 7 introduced Direct2d as the faster replacement, but you can still use GDI today.