Cycles has no motion blur on animated shaders

I’m using a refraction BSDF shader to get a heat distortion effect for a sci fi thruster. I’m animating noise and using that for the normal, IOR and roughness to get a heat distortion effect, but I also want it to have motion blur. When I render it, though, it has absolutely none. I tried plugging in a checkerboard texture to really see if there was any motion blur, but still nothing. Does cycles not calculate motion blur on animated shaders? If not, how can I get around this?

Blender can deliver a speed Vector pass in View Layer Properties → Passes → Data.
Haven’t used it yet mysel. Mavbe have to composite in post prod.