YouTube lets some channels upload 8K at 4320p. I’m not sure what the qualifications are to upload 8K, if any.
Sony trademarked a 4K logo (specifically an HDR logo), but does not have a trademark on what “4K” means in written form. “4K” always has to be qualified, because even within DCI there are three 4K resolutions ranging from scope to full container (different vertical heights). Broadcast TV has its own 4K definition, and Blu-ray has yet another set of 4K resolutions because DCI 4096 movies get scaled down to UHD 3840, but usually not the full 3840x2160 since DCI movies are wider-screen.
As for the OP, his opening screenshot had 3840x2160 which should qualify as 4K on YouTube. Other people online (Reddit) have reported that their video was randomly skipped for 4K conversion. They deleted their video from YouTube and reuploaded, and it worked the second time without doing anything differently. Not sure what to recommend to the OP… looks like he did everything right on his side.