To clarify, we are discussing two separate issues here:
(1) How to display "option"-types in callback signatures. A bug in the XSLT meant that no type was displayed at all. I have fixed this in the grunt-jquery-content project and sent a pull request.
(2) How the second overload of jQuery.map should be documented. I believe scottgonzales is correct here, and the second overload should only concern object-types, since arrays are covered in the first overload. So there is no "indexOrKey" parameter, it is just "index" in the first overload and "key" in the second. I have commited a fix for this.