It's possible there's some reason like that for the diverging timelines, some part of the data gathering process.

[He definitely wants to compare timelines, to find out more. He's worried, now, if she's from some time before him... then he might not know what really happened.]

They don't use any recognizable patterns for that... the same goes for the people that are drawn here. Sometimes it does seem to come in waves, a few people at once from one particular universe. But sometimes it might only be one at a time, and some people end up being the only one from their place and time. A lot about it appears to be randomized.