Hi,
my guess is that a RWR was never used to shadow/detect ships. Indications for this are: a) I have never seen any source mentioning such a use, b) bearing information would be very important for this and it seems that bearing information was never much of a concern in the development of RWR, and c) ship's radar was always ahead of airborne radar in terms of wave-lengths.
If my guess is true, my workaround with the RWR height simulates real-life performance quite well ---> there are more important issues to tackle
Regards, LGN1