Not double pass

How often in professional go (囲碁) does one player pass, and the next player does not pass, but plays a move probably attacking a group the first player thought was safe?

This appears to be the crux of the difference between Japanese and Chinese scoring. Under Chinese scoring, a player may "shore up" his own possibly weak groups at the end of the game with impunity. Japanese scoring encourages players to leave their groups just barely living to maximize the amount of enclosed territory.