not quite. Mipmapping itself is the process of creating various versions of a texture with different resolutions for different distances, so you don't use a, say, 2048x2048 texture in a mile distance where nobody would see the detail.
Now without mipmap dithering you can see "jumps" in texture detail (good to see on DMAriza's floor textures). it's like you see a horizontal line where the higher res texture ends and the next lower texture begins.
I dunno how mipmap dithering in detail works, but it supresses this effect and smoothens out the transition between different mipmap levels.