Score header and top-level markup

[Simon Albrecht]

Hi everyone,

%%%%%%%%%%%%%%%
\version "2.23.9"
\bookpart {
  \markup \fontsize #10 "general title"
  \header {
    title = "specific title"
  }
  \score {
    { 1 }
  }
}
%%%%%%%%%%%%%%%%

why does "general title" appear below "specific title" and not above? 
How can I change that?

Best, Simon