Final Cut Pro subtitle coordinates are not as expected when the project is vertical

When you add a title to a 1080x1920 project, if you move it up and down, you will see the *range* of values is -540 to +540, NOT -960 to +960.

All Motion template media is measured with a vertical dimension of 1080... ALL OF IT. Images, video, drop zones, titles, generators, everything.... Any project size. Any aspect ratio.... anything added to FCPX via Motion template has a vertical dimension of 1080.

All widths are 1080 x Aspect Ratio, in this case: 0.5625 (1080/1920).

If you multiply 1080 by 0.5625, you get: 607.5 which FCPX rounds to the nearest whole integer. That gives the horizontal dimension the range of -304 to +304.

That's the explanation... not sure if it's going to make sense.

Did you try using the Transform tool in the Video pane, instead of the Text pane?

AFAICT, this always gives the expected result (at least it did in several times that I tried).