Ok I have been doing more tests and it seems that Maya's cached playback, when turned on, causing the fibers not to activate. I only happened to turn it off due to Maya acting stupid with the alembic cache of the bones. Then the issue seemed to be solved.
Perhaps Ziva can only use the curve's length when it is actually shorter in the viewport, rather than Maya telling it on frame 'x' it is 'y' length. Since I was still on frame 1 while it was caching the whole thing, the curve never changed.
I think I know why, in my first video, the fibers seem to activate instantly towards the end. This could be because, when Ziva's RAM cache was far enough for me to skip forward to see what was happening, when I did skip forward the curve was shorter, instantly activating it from 0 to wherever I skipped to.
Good news is that Ziva's RAM cache still works fine with Maya's cached playback turned off. I just have to click play to store the RAM cache rather than it just doing it by itself, which I prefer anyways.