I have read the sometimes there will not be enough acid in the recipe to react with the soda so adding more will help with the rise. If using baking soda and acid, the batter needs to get into the oven ASAP too since it starts rising before the heat hits it-- and if it sits for a bit, none of that dropping on the counter to remove air bubblesI think they meant for the buttermilk trade out.
Like when you don't have buttermilk but can add some lemon juice or vinegar to regular milk to "make" buttermilk.
I know in GF cooking some recipes call for an addition of powdered citric acid or vinegar as stand alone ingredients however they don't have baking soda even in them.