The fact that some people cause it and some people don't (the coin flip bias) can have an explanation something like having to do with their impact on the causality chain if our universe/timeline. It could be anything from which one of them is older, to which one of them has a future offspring that does something big that has a big impact on the universe (in terms of Butterfly Effect kind of knock-on effects).

But I just don't see a person being able to flip accurately enough cause this. No way. But I'm just playing along here. I don't truly believe this experiment is anything but either a hoax, or mistake.