I don't have any problem to understand that the back ground or fore ground can be nervous , but here are the 2 lenses compared at the same distances and there are several distances.
But neither of them reveals anything like this:
Your "several distances" are too short. You concluded that both lenses have wonderful bokeh, which is incorrect in many situations. They typically include shooting half-body environmental portraits, not miniature toys; and not always wide open.
Pi, ankorwatt says, and pictures prove that, the Sigma has not worse bokeh, than canon has, despite it has less CA and is sharper - optically better. No more, no less. And no one says the bokeh of 35 mm f1.4 lens is as nice as 70-200 f2.8 II or 135 f2 for example. But from 35 mm f1.4 lens bunch it is the best one.