In culinary school they teach you "the proper way" to do things. For everyday use their way is usually impractical, because it wastes a lot and takes much more time to do. If you are tired and short on money, do you really want to take more time to do something, and also waste a lot of what you are using? Not really. But for onions, I have found that the way they teach you in school is probably the best, fastest, and you can choose to not waste the "imperfect" cuts.
I hope this helps!