fwiw, I was actually annoyed that the function does not take that many arguments, if I am not missing something.
The extra arguments are used as identifiers within the function. It's a common trick to save a few bytes since you get function scoped vars without needing the "var" keyword.
yes but it's not needed in this case, they could have reused existing variables and since clarity is not a goal (given e.g. "s=document") it wouldn't be an issue.