Why is FCPX creating a second YUV video track during the share process?

Some background and context - first, I know that my OS and these versions of the software are no longer supported, but surely someone somewhere can help me figure out why FCPX is creating a second YUV video track:

I have created settings via Compressor that I can use in FCPX

Which allows me to use them in FCPX, via the File> Share> Add Destination

Double click on Compressor Settings and they are available for me to add to the Share menu

After the .mp4 file has been completed successfully, MedioInfo reports that there are two video tracks, which filmhub.com will not accept a file with a second video track

I know that I can run the following ffmpeg command to delete the second video track:

ffmpeg -i Not-if.mp4 -map 0 -map -0:v:1 -c copy Not-if-one-vid.mp4

Which results in one video track:

but I want to know what I am doing wrong or what I have to change in Compressor, that would cause it to stop making a second YUV track

BTW, I thought this issue might be avoided by selecting "none" for Embed CEA-608 option, under the Settings tab, but that did not change the outcome

Please help me understand and thanks in advance

[Edited by Moderator]