These are some results after I've working around with physics without vsync.
1. The random calculation is actually pretty big if your game is physic based. For example, my game, enemy uses jump attack (of course using physic action) and mostly they remain in the screen safely. However, sometimes it flies away from the screen like it had a rocket behind it. I just put only one apply force event for them.
2. After disable vsync, normal physics is being calculated randomly as well. And it requires too much number. It was like 1000 physic force before, but I needed to multiplies it seven times in order to make sense. So 7000, it's really pretty big math.
There must be some stability update in order to make dt based Physics does not calcurate random number much. Otherwise all games deal with Physics switched off vsync will face some frustration for players.
P.S I think the physics goes faster when memory being used a lot. And slower when it doesn't.
P.S 2 Funny thing is bullet behaviour's physic(gravity) works well no matter I've messing around. Of course, there is some random gravity. But it's only small, unlike physics. This should be true random calculation standard....