Please take a look at the film linked below.
In it you can see the same motion blur experiment, rendered with Eevee & Cycles.
Could anyone tell me why Eevee’s blur stays true to the path it actually took across the screen and Cycles doesn’t? Does anyone know a way to make the Cycles motion blur have the same geometry as the Eevee MB?
(the cycles version is slightly different in that i animated the shutter a little at the end, but this doesn’t effect the general nature of my question!)