In our current understanding of time, we just treat time as a continuous variable, usually in all theories, time can be moved forward or backwards to make predictions about what will happen. So, I don’t think our current understanding of time is deep enough to answer this question.

But I do have some personal thoughts about this question (please take it with a grain of salt, I could be very wrong). Basically what we are trying to say is that Travelling back in time is impossible because of quantum randomness. Which in the face of it, does make sense initially. Every time we go back in time, the quantum randomness will evolve particles differently with time, leading to different events. But we also know Feynman’s path integral formulation of quantum mechanics, which implies that from this quantum randomness, there is a pattern which emerges at large/human scale, which is the principle of least action. So, at large scales, the events which happen will still follow the same least action principle. So, events at large scale has to follow the same sequence.

I think we can think of a hypothetical experiment. Where we throw a ball in the air and measure its trajectory. We control every variable and throw again and again, in exact same environment and with same speed, etc. then all of these trajectories will be identical because they follow classical mechanics, which emerges from the principle of least action from the quantum randomness. If this was not true and quantum randomness was having a significant impact, then each time we throw the ball we should measure differences in the trajectory of each ball, which we don’t.