As I understand it from the outside, it is now official Church doctrine that the particular prohibition that was universally understood to apply to coffee and tea but sometimes interpreted more broadly is limited (in the strict sense) to coffee and tea (the latter, I believe, in the strict sense of drinks made from Camellia sinensis), but that rather recent doctrinal clarification did not erase the fairly strong tradition that the prohibition in application should be treated much more broadly than it's express limits, even if the Church does not specifically dictate the precise bounds, and so the widespread (though not universal) practice of abstention from caffeine as a stimulant prohibited by the broader prohibition in which the specific prohibition now deemed to mean “coffee and tea” continues.
This isn't inherently regional, though variations in the practice probably have some loose correlation with geography.
This isn't inherently regional, though variations in the practice probably have some loose correlation with geography.