it's mind blowing but to me, we judge the concept of 'time' and 'space' under our own human rules and limits, but the perspective of the whole universe, so to speak, is very different and far more complex and there is not such a thing as a definite past, present and future because everything, in a way, exists and 'happens' simultaneously. Therefore, it doesn't matter if from our perspective (that is not wrong, but it's only one of the many) it was Nero's intrusion that created this reality (=the moment it became different it became parallel to the other), this is a parallel reality and there might be differences that go beyond the point of his intrusion. For this reason, I'm not too stuck with the logic that we must see different things only at the point of time after Nero, for me this is another reality point period and as such there might be differences.
It's also wrong, in a sense, to think about tos being 'default' and Nero changing how things were supposed to be. From a wider and more generic perspective, there are infinite realities and tos only was one of them and you could even say that the lack of intrusion by Nero in the other had modified/changed that reality too by, essentially, not making it like this one.