Why does write-region use message_with_string?

[Jorgen Schaefer]

Hi!
I'm trying to intercept all output from emacs -batch from within lisp.
This works nicely with a defadvice around `message' and `princ', except
in one case: write-region.

In fileio.c:4995, this function calls message_with_string directly,
circumventing lisp completely.

Is there a particular reason for this, or can this be replaced by the
usual message functions?

Regards,
Jorgen