Just because something is academic doesn't mean it's not worthwhile. For instance, map, keep, reduce, etc. are different if passed a function with side-effects. What happens if you give them a function which modifies the list as it's being traversed? A pathological example:
However, if map is passed a pure function, you can e.g. run one copy of the function on each core and run it in parallel.
And "dangerSet" is both non-Lispy and non-Arcy. It's non-Arcy because it's long. And it's non-Lispy because of that capital letter: danger-set would be marginally better. But nevertheless, pair? is shorter than is-pair, and (in my opinion) reads much more nicely.