I wouldn't say, in particlar, that the exercise is to show competence in flying at Vmca - it's more to show why you SHOULDN'T fly at, or even near, Vmca.
It highlights the need for flight at or above "blue line".
I, too, would have "ticked the box VMCA tested" - the lesson had been demonstrated (fairly well, I think).
Now imagine the other scenario - where none of the crew of that aircraft had ever done spin recovery training.
I would also say that ALL aircraft are capable of spinning - they're just certified for doing it intentionally - but that's a product liability factor, not airworthiness.