> It looks like kernel doesn't notify userland when a redirect route is
> deleted due to timeout (on the other hand, it notifies when it is
> created or deleted manually).
> 
> Is there any reason to do so?

Let me turn the question around slightly.  Do we know if any existing
routing daemons would be confused if they started showing up (i.e.,
would it start publishing host routes or something silly like that?)