Ok, more weird than I thought.
Appears the god doesn't turn hostile, and joins my side of the fight..
My ships don't engage normally - like they're escorting a friendly ship.
But they are firing all weapons and the god is slowly dying without return fire.
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2810862882

Hmm, sounds like some of the underlying script for that event needs updating.

Have noticed in the past that the AI often will gain the system anyways even where you the player would have to fight the thing. Sometimes the Edo Guardian is gone, other times its still around.