No, it just depends on which RFC you follow that describes URL escaping.
Which? In JavaScript used encodeURI for URL and encodeURIComponent for single components. hunchentoot:url-decode does not match any of these functions. Browser does not replace # + to "%2B" in header when sending request to the server. A substitute # \ + at # \ Space, as does hunchentoot:url-decode, need for forms, but not for the url.
I have wrong understanding?
Andrey