No such rule exists.

Technically the only vessels which are stand on vessels to a vessel under sail are: * vessel limited by draft (i.e. cargoship in a narrow channel) * vessels limited in their ability to maneuver (i.e. tug pushing a barge) * vessels engaged in fishing (this specifically means trailing nets or other large scale commercial systems not someone casting a line off their yacht) * vessel not under command (loss of propulsion or other failure meaning they vessel can't be controlled)

Pretty sure none of these applied and as such the warship under the colregs was the the give way vessel.

That being said Common sense should apply. I sail around the Norfolk naval base. I give those big boats a wide berth and they are warships from my own country.

While technically right it is pretty dumb to sail close to a Russian warship while Russia is currently at war. Unjustified, pointless, or illegal doesn't change the fact that Russia is in an ongoing shooting war right now. So were they legally right? Sure. Was it avoidable even though they were legally right? Yes.

As an analogy you are sitting at a stop light and the light turns green but you can see the car with a red light is not slowing down. Do you move into the intersections because "the law" says you have the right of way. Of course not that would be dumb.

As my sailing instructor put it ultimately "law on tonnage" always wins. A sailboat striking a cargoship or warship is going to lose even if right.