Well, we're talking here about very concrete things: days where cyber activity is stopped as a show of good faith, or nations trading their compromised networks

Well, we're talking here about very concrete things: days where cyber activity is stopped as a show of good faith, or nations trading their compromised networks like they do today with spies. This won't in and of itself stop the activity - and it's not intended to. This is intended to foster cooperation and trust. Cooperation and trust are required for international norms development and cooperation on standards, and in addition lessen the incentive for nations to hack one another out of suspicion or hedging bets.