The kata descriptions tend to be the most generic possible, so it's expectable there are some differences between the description and the kata in some particular languages (not all languages have tuples, naming conventions are different...).

The "Clever" upvote.

The answer is simple: it does not.

Definitely not best practice.

for the simple ones one liners are probably actually better solutiions, and here on codewars making things into one liners is more of a sport

Oh, young padawan, a real one-liner, you haven't seen

Agreed - there should be a reasonable compromise between readability and concision when programming. Given this Kata, I'd personally understand a piece code much better if it wasn't indeed crammed into a single line, where the reader has to put so much effort in trying to decipher and understand the "cleverness" of the code.

Counter creates a dictionary, which is more convenient and is also faster.