Good information.
It's good to know that it isn't a bug with the actual game engine, but rather something that SCS put in for gameplay reasons. I'm pretty sure that's it, because the sensors can detect those objects, meaning that the AI could be made to fire on those detections, it's just that the game is hardcoded not to give a detection for AI platforms. That's my guess anyway.
SCS made some "interesting" gameplay calls with DW, so maybe they put that there so that players could fight ASW aircraft from submarines, the same reason they put in the SAM launcher in the first place, but they figured that in MP, air players wouldn't appreciate that.
My point is that before we get all mad at the game and start using words like "bug", "cheat", etc. it's good to have an understanding of what's entailed in producing the behavior.
Maybe I'm just sensitive to negative emoticons.
