Er..., contrary scales are mirror images. The movements you do with one hand are exactly duplicated in the other. They are a lot easier than parallel scales where the fingering is in fact different. One hand can train the other.Of course, all this falls apart when you play them out of sync.
The rest (Bb major, Eb major, Ab major, F minor, C# minor come to mind) are not and can be quite nightmarishly to co-ordinate. With non-standard fingering, only C major is mirror like.
You are right (of course). i must have been in my contrary-parallel universe when I wrote this That goes to show how much I practice contrary scales...
Now that you mention it, I cannot remember any piece that actually has contrary scales (except for etudes) in any extensive way.