Comment (by Roland Haas):

note that "" matching anything is as documented, https://einsteintoolkit.org/usersguide/UsersGuide.html#x1-187000D2.3.2

Allowed values for strings should be specified using regular expressions. To allow any string, the regular expression "" should be used.

--
Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2939/ahfinderdirect-range-options-for