I think there's a disconnect between the specialist reference guide and in-game stats for King. Maybe a tweak that was made but not updated in the guide?
Guide:
Destroys 1 enemy driller for every 3 of your drillers that participate in combat.
Game:
Adds 25% to owner's driller count in all combat.
I'd appreciate a math check, but wouldn't that be destroying 1 for every 4?