I am an ex-professional ballet dancer, and one of the things I always find interesting is that any experienced ballet dancer can instantly tell who trained as a child and who didn't solely by how they stand (literally not even moving) at the barre. But the thing is, children with only a few years of training under their belt will often show this good form, while I have literally never seen someone who started as an adult, even dedicated adults who take class 4-5 times a week, get rid of that "I started as an adult" posture.
As an example, I was actually quite impressed at how Natalie Portman really managed to "look the part" in her role as a ballerina in Black Swan. Still, she wasn't fooling anyone with training - even with just a simple port de bras (raising of an arm), you could easily tell she wasn't a dancer.
Which is interesting, because from what I can tell she studied ballet from a young age, which potentially puts a hole in your theory. Unless you're only taking about professional dancers who started young versus professional dancers who started late, rather than any (i.e. non-professional) dancer.
(also: ex-pro ballet to HN? Can't imagine there's much crossover in that Venn!)
I've tried emulating those movements, and just look like Bullwinkle.