Well now Bruce, thanks for the video, but I must say that it does nothing to harm your earlier premise, as a smooth, straight, level and pre-existing road that has been covered with a well spread load of fresh material of even consistency is hardly a worthy test for either of our views!
What I will take from that video is the obvious "lightness" of the machine, and how if you were to try and get aggressive with it, it would clearly just buck and skip over any real resistance. If you were to get it to dig in to any significant degree, it would almost certainly stall the horses, or early weak tractor, that was tied on out front. Of course much heavier, larger graders of the type did come along as time passed, but they were still pretty light compared to a well stuck rock, large roots or other "fixed" resistance, while already deflecting a blade full of dirt.
I am equally sure that back in the day, there were masters of the art, that could "work" the machine in a manner much more like what you had envision, but my feeling is, that wasn't the norm by a long stretch.