Kevin,
Here is what I found:
I looks like the baseline locks to the “center” of the text block.
So 1 line of text centers your text on the screen. 2 lines of text will push your first line up from the center base and your 2nd line below.
You can change the baseline in the text editor window or simply by using the position X/Y controls in the filter.
I tested this back to FCP 5 and it works the same there.
I’ll run it by Boris / Engineering to make sure this is expected behavior but I believe it is.