Should 'filter' really apply to <mask>?

Should 'filter' apply to the <mask> element itself (as currently  
specified)? I've tested in Batik, Firefox, Webkit and Opera. None of them  
applies the filter to the <mask> element (of course it works fine when  
applied to child elements of the <mask>).

I suspect this is a similar issue to the 'opacity' property, that we  
clarified in SVG 1.1F2 to have no effect on the <mask> element.

I've attached an example testcase.


-- 
Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed