^As I said above, there's no remotely plausible way that any action taken 250 million years in the past could make such a subtle change to the present as a single individual having a different name and personality and a single organization being differently structured. A change that far back would've either had no effect at all or prevented humanity from ever evolving. So there's no point in expecting any kind of consistent logic here, since it never made sense in the first place.
Maybe it wasn't Nick and Helen's actions in the past that caused a change in history. Maybe the anomaly they passed through simply had some kind of dimensional hiccup and deposited them in a slightly different timeline than the one they left, one that spontaneously arose on its own far more recently. Like if you travel a long distance down the highway, then come back and accidentally take the wrong exit close to home. After all, quantum physics says that alternate histories may be spontaneously emerging all the time. Indeed, theory suggests that, contrary to what we assume in fiction, time travel couldn't
create an alternate history, because your quantum entanglement with your own timeline of origin compels you to take only those actions that would bring it about. So any alternate timeline wouldn't be something a time traveller caused; at most, it would be something that already existed and they found a way to visit. It could happen if there's some sort of nonlinear quantum process taking place in the anomalies. They could be passages between timelines as well as times.