I mean I feel like it can be a little more complicated than that. I think this standard is most relevant for top lane since positioning determines if you lose a trade which is typically melee. In mid lane there's typically skill shots thrown around. The only thing to really learn in mid if you're playing a skillshot champ to farm is to learn how much your skill shots will do early and then finish up with last hits.
I can pick up any new champ and cs just about the same but my limited knowledge of that champ means I'm not likely to get kills in lane and I won't be as confident in what I can do in teamfights.
For me anyway it doesn't take more than 4 games at the most for me to understand how to cs properly but I can't call myself decent at that champ until I'm confident in those two other situations.