The Macallan is kind of a special case of sherry barrel aging nowadays. Because of US laws that require aging bourbon in new, freshly charred, American oak barrels, a large quantity of the barrels sold to distillers across the globe are "ex bourbon." So, now, an awful lot of booze out there -- and not just whiskey, but also American brandy and some Caribbean rums -- tastes sorta like bourbon.
Lately it seems like there's so many sherry-aged whiskies and whiskey-aged something or other, or first-fill, second-fill, ends up traveling over three continents. Seems like the barrel coopers are the ones doing the best, but even then the wood itself is pretty contentious in terms of quality versus hype.