I would say that even "hardened mercenaries" couldn't "use the tactic" because characters do not go around with class labels and status effect indicators floating above their heads. All the goblins see is a big guy with an axe.Essentially ending the encounter by having the goblins flee, or cower, or surrender is fine.
Having the goblins respond with advanced tactics tailored to take advantage of a very specific short circuit to the rage ability requires some in game justification, in my opinion.
Hardened goblin mercenaries that have fought in many wars over the years, could plausibly know the tactic. Others, probably should not.