It's absolutely an achievement. It takes a desire to actually build hydroelectric power and the will to put it into place.

Washington state could be hydro powered, but it's only 70%, with 20% non-renewable. Quebec is 97% hydro, but 3% nuclear due to a historical political horse-trade. Illinois, despite having the mighty Mississippi River, has 3 total dams and is less than 1% of its energy mix, with more than 50% being non-renewable.

So Costa Rica and Tasmania do enjoy some advantages, but so do lots of other places that haven't accomplished the same.