I think it is this "roughness" that causes the neat patterns on the cushions and this roughness isn't there in the reflections. So it seems it's not the velvet node but the other nodes in the shader that aren't visible in reflections. The other nodes are noise, clouds, fractal sums, and a lot of mathematical operations. :(

I rendered the original with Raytrace Depth of 5, but also samples with 12, it made no difference.