No STATUSTEXT messages via uart/mavlink?

The STATUSTEXT message (#253) provide warnings (such as prearm: …) in plain text (50 char).

I wanted to grab them by my osd board, but that doesn’t work.
Sending this message should not depend on a stream request - or does it ? If so, which stream should be requested ? If not, what has to be done to make the pixhawk send this message ?