While drawing say, a rectangle, if I go to the edge the display will scroll but all the artwork on the canvas shows up broken until I let go of the mouse, at which point it redraws correctly.
When drawing with the pen tool, and adjusting a curve point, if I go off the edge the screen scrolls while also rendering correctly.
Clearly, the rendering engine is capable of redrawing the canvas while scrolling with a drawing tool, since it works exactly as it should with the pen tool. Modern computers are obviously fast enough to handle redrawing, especailly with the faster graphics engine in CS6.
Also, people have been asking for this for like a decade now.