I guess I will have to differ with the Pool School there.
I much prefer to add exact amounts of what I need of only the ingredient I need. Kinda like taking a multi-symptom cough cold sinus medication...sure, you get what you need plus other stuff. I take the individual products as needed, not the multiple symptom products.
When I set up my pool this year, the water had a green tint straight out the hose! Immediately began bleach dumping, no way was I gonna start off like that! While shocking the new water, I calculated the CYA dose and had it ready. I did not want to confuse the initial shock CL test readings by adding the CYA at that time, even if it meant I used more bleach. Once the shock was done, I applied the CYA and let the CL fall to my target level {5-7}, and added my baking soda, borax and muriatic acid as spec'd by the calculator.
But as long as you get to a sparkling pool to enjoy, let's do it!