Why does FCPX export 4K at 1920x1013?

I'm shooting video with Fuji X-H1, recording clips in 4K at 4096x2160. I'm not doing anything with the footage other than colour grading so there's no other transformations applied etc.

My problem is: Exporting to 1080p only gives me an option of 1920x1013 and I get black bars at top and bottom of the clip.

How do I fix this without cropping in? Is this even possible?

I have noticed that downscaling to 3840x2160 gives me an option of 1920x1080 but the exported clip still displays black bars.

Project settings:

Actual clip in timeline 'info':

Export options:

It doesn't make a difference if I change from 'Apple devices' to other export targets. So just clearing that up before everyone jumps on that bandwagon. The export intent is for screen projection in church not for web use.