Mysterious context creation

[Mats Bengtsson]

What happens in the example below?
The lyrics line appears above the music staff 
as soon as I add the property setting.

I know the solution, namely to explicitly create
the Staff context, but I can't understand what's
going on.

      /Mats

\version "1.3.113"
\score {
  \addlyrics
    \notes\relative c' {
    % The following line makes the lyrics appear above the staff!
    \property Score.TextScript \override #'padding = #5
    % Changing Score -> Staff helps, 
    % so does an explicit \context Staff declaration above.
%    \property Staff.TextScript \override #'padding = #5
    c1^"abc" | 
    d^"def" 
  }
  \context Lyrics = mylyrics \lyrics {
    Text text }
  \paper{}
}