I'd imagine not a whole lot.I wonder how many single players know that?Or, its just poor wording on FXS part as there are several other promotions that require the player's promoted unit to be the attacker in order to be triggered, but only say "vs.". (e.g. Volley, Spiking the Guns, Advanced Rangefinding, Marauding, Line of Battle, etc.)
Yep, just another piece of info hidden from the player by poor wording/UI. Unfortunately, this means the only way to know about bonuses received (or, not received) when on defense, without looking at the game files, is to find an AI unit with the appropriate promotions and check the combat preview. Maybe one day I'll get to actually modding in the text changes (There's a whole slew of incorrect & missing info in the text files.), but it'd be nice if FXS did so first.As @Sostratus points out, we only see the combat odds calculations when we're the attacked. Based on the "vs." text description, I just assumed the bonus applied always, as we never see the odds before we're attacked by the AI.