The term 'huckleberry' is American, deriving from the older English hurtleberry/whortleberry (Oxford English Dictionary). I can find no evidence that the earlier terms were used in this capacity - which appears to be an American nineteenth-century innovation. It seems we can, therefore, disregard the medieval explanation provided in the link you provide.

This site provides a credible discussion of the word and how it came to refer to someone who was just right for the job. The huckleberries were small and of little consequence - apparently Twain's inspiration for naming his character Huckleberry Finn, a poor boy who was of less consequence than the socially-superior Tom Sawyer (according to Twain himself). As the discussion provided in the link indicates, transforming the humble huckleberry into a name for someone perfectly fit for a specific task is another matter, but it appears to hover around the idea that "I may not be suited for everything (i.e., I may not amount to much), but I'm a perfect fit for the task you want performed."