Ok, I'm not good with words, but here goes. Maybe someone can explain it better and feel free to correct me if I'm wrong.
One reason I'm not sure if the pokemon showed on the first page is real, the water otter pokemon. It's second evolution stands on two feet with two arms. While its final evolution walks on all fours.
So by looking at the pictures, it seems that the second evolution would be capable of learning an attack such as Ice Punch. However, it's final evolution wouldn't be capable of learning something like this because it's on all fours.
Basically, by evolving, it looks like the otter pokemon would be losing out on some moves, something that's never happened in previous pokemon games.