whiteout on stems?

[Graham Percival]

Is there a bug in  input/regression/whiteout.ly ?

In 2.11.22, I see ledger lines whited out, but the note stem is still 
there.  The texidoc says

\header{
  texidoc = "The whiteout command underlays a white box under a
markup.  The whitening effect only is only guaranteed for staff lines,
since staff lines are in a different layer.  "
}

Should the second sentence be "... is only guarenteed for staff lines, 
since **stem lines** are in a different layer." ?

Cheers,
- Graham