That doesn’t seem to do anything. Here’s with (0, 1, 0):
and here’s with (0, -1, 0)
In both cases, the light is positioned at 100 and in both cases the light appears in the same place rather than in the (0, -1, 0) case the light being closer to the bottom as I was expecting.
For reference, if that was doing what I was hoping for, it would look like this:
(I manually set light position to -100)