NS font case sensitivity

[Jason Rumney]

I just now came across this snippet in font.c:


     Lisp_Object alters
   = Fassoc_string (val, Vface_alternative_font_family_alist,
#ifndef HAVE_NS
            Qt
#else
            Qnil
#endif
            );


Is there a good reason why the entries in 
face-alternative-font-family-alist need to be case sensitive on NS when 
they are not on other platforms?