I think that falls under “a difference in the number of non-pass moves”. But it is indeed a way to get that.
I suppose there may occasionally be additional (usually minor) differences due to “no points/territory in seki” under Japanese rules when there is a seki with an unbalanced number of false eyes.
Don’t forget about unremovable ko threats, which can change the life&death status of a group between the two rulesets for an arbitrary number of points. 
True.
Still it is fairly uncommon that, with optimal play by both players close to the game end, the Chinese and Japanese net scores differ by more than 1 point.
YEAH I KNOW! I was talking about netral spots which in if you put a stone there, it will count as a alive stone and a score in Chinese scoring.
Can you explane more about this part? what is “dame” or what do you mean by the phrase in () ?
like dame?
When neither player can increase their territories anymore, the game is nearly over. But there may still be some empty intersections left between the territories. Those are called “dame” in Japanese, or “neutral points” in English.
Filling dame near the end of the game
Under Japanese rules, this doesn’t change the territories (and thus the scores), so it doesn’t really matter which player fills the dame. But it is still good practice to alternate filling dame before stopping the game.
Under Chinese rules you can still increase your score by filling dame, because it increases your number of living stones without decreasing your territory. So it’s advisable to fill as many dame as you can before stopping the game. Still, if both players fill the same number of dame before the game stops, the net score will stay the same.
Playing inside your territory after all dame are filled
Under Chinese rules those are useless moves, but your score doesn’t actually change, because you increase your number of living stones by the same amount as you decrease your territory. Still, it’s not considered good behaviour if you do this and it can be reported for “stalling”.
But under Japanese rules you lose points doing this, because it decreases your territory and you gain nothing in return. So it’s worse than useless under Japanese rules. Better just pass to stop and score the game.
thank you.