Rules as Written. Short hand for not including house rules.
I agree. Concessions should be the PC or NPC doesn't get what they want and should make sense in the story. When my NPC's concede, it's usually running away(I tried to have one beg for his life, but the PC's just executed him), and I ask if the player will pursue. If the players pursue, I don't count it as a concession, if they don't, then I do. When my players concede, I listen, if it makes sense, I'll agree, if it doesn't I say no, then ask the other players if I'm being to harsh.
Concede shouldn't be a get away free button, unless the opposing party is content to let them run.