It seems to go further. They must be intentionally adding ingredients that have a high sugar content, else they would never get to the 21g of sugar in a 21oz drink, as mentioned by the article.
Either way wouldn't the greatest satisfaction of a habit-forming desire come from those who are having a little metabolic shortage at the time for one reason or another?
Starbucks has always been completely dependent on habit-forming behavior in response to significantly powerful substances.
That's what dependency can do.
My carton of regular milk says 11g or sugar per 240ml. So seems like simple milk could get there.