I am all for students having a sound understanding of the relevant theory, but not all theory is equally important. In the case of Vmc I think entirely too much time is spent on configuration trivia and pedantry over definition and far too little time on the practical operational significance of the published Vmca and the concept of Vmc in general. In other words it is assigned an importance in the training syllabus that exceeds its value.
Even though I believe that teaching the correct/current definition is important, I definitely agree with your comment. What Vmc means while operationally flying needs a bit more spotlight time.