Common Sense: Working memory imbalances don't interfere with working memory in every circumstance, they only gum up the works, like molasses in January.
One of the main reasons some of the stimulant meds don't work effectively is that they don't cover every essential neurotransmitter system necessary for efficient pre-frontal cortical communication.
This brief video breaks down an essential difference between amphetamine [AMP] and methylphenidate [MPH] stimulants. In 4 min and 50 sec I break down the serious metabolic details for those important medication matters.
Let's face the naming thing squarely, head on. ADHD and ADD labels provide more confusion than understanding, more complexity than common sense. Why, because they describe symptoms that remain on the surface.