But you can at see how this sequence of “w a1, b a3, w a2, b pass” can be repeated over and over again without super-ko rule? (w can play a1 again after b pass)
See how black captures 2 stones where white only captures 1, so under japanese rules this sequence would be +1 point for black. So under jap rules, with enough cycles black could pass instead a3 and allow white to connect (thou b have to play c1 because stones are in atari)
But since chinese area scoring ignores all captures, and only counts the living stones and territories, this whole sequence is ±0 points for both players, because the board does not actually change at all.
Now imagine game being really close and black having only 0.5 point lead after all ‘proper’ moves having been played. If white would decide to start playing this cycle, and if black would not take a3, but instead play c1 and allow white to connect a3, this would mean white gaining 1 point by turning dame into living white stone, while b does not gain anything by turning 1 point of territory into living stone. White would win, so black would always have to take at a3 after w a1 while w could just play the cycle again and again.
For this reason chinese rules have the super-ko rule, it is to prevent that specific situation.