Mixing them together causes an exothermic reaction that releases a lot of CO2. Both the heat and the releasing of gas bubbles can also help to break up things. Also it’s unlikely that all will mix with all, so you get some pockets of basic and some pockets of alkaline, who knows what you’re trying to break up but some of either might help. The method they learned is kind of throwing everything at it cus something will work. You aren’t wrong, both methods have validity