I only dabble in graphics - but generallly simple edge detection needs really uniform tonality and no textures in the input to work well. Look for example in the more "sketchy" examples how the linework that "looks right" is extracted from a quite noisy input. Also, in the top example where there are houses, the contrast difference that gets extracted to linework is lower than in the character areas.

So, the flat shaded images with explicit black outlines - yes, it's likely there is much difference with edge detection. But when the image has lots of different contrasts and tonalities this looks much more impressive.