Text is wrong, but the effect is intentional; one of the battlefield promotion modifier triggers is killing the player but with extinction enabled that would end the activity; so you'd be getting a free +4.
Same reason if you pick heavyweight/special ammo increased it will prevent you from using the 3 famine options (or vice versa)
You'll not really encounter many promoted enemies besides the default spawns due to the activities not really having 2 factions fighting; its a free +4.
If its you vs them - you die the promotion is meaningless anyways.
If its 2 factions fighting in an area + you, that rarely happens in the activities we have so they will rarely be able to trigger that part of the modifier.