I agree with everything you wrote, but assuming that micro differences in angles are not practically important, I believe that developing the ability to do it exactly the way that you intend to IS important. I was working with two guys last night on the Mook Jong and pointed out that their arms are essentially the same length as one another, but their waists were 4" different in height, meaning one had significantly longer legs than the other.
That means, that to position themselves optimally on each section of that form they will be in different places, so we'll all work through and find our sweet spot. It's not about being in the "correct" spot for authentic Wing Chun, it's about knowing your own body and having command of it to position yourself appropriately. Unscripted, you can't be calculating angles, you have to focus on the macro and find a way to win. In a form, like the Mook Jong, I want them to strive for perfect position, perfect structure, perfect expression.
But, that's just me. I do agree with what you wrote above. They are not contradictory ideas.