Cycles - Surface displacement not prompting motion blur

Hello, I’ve been trying achieve an effect discussed in this video:


enter image description here

The point is that normal displacement is cycled to one cycle per frame and then the displacement appears static thanks to motion blur, and simulates brush strokes:

I’ve managed to come close to rendering this effect by using displace modifier and cycle between different scales:
image

However the correct way to do it would be using displacement node and control texture coordinates, which I’ve set up as well:


I then cycle with changing UV coords:

The problem is that unlike with displace modifier where the motion blur achieves the desired effect, it doesn’t do so when using the displacement node:
image

It seems like changing displacement via displacement node does not prompt motion blur. I would be glad for any help in figuring this out. I’ve also posted this question on blender exchange:

Thanks in advance