Uncompressed. I just tried one on medium, same result. It uploaded successfully, but doesn't appear compressed. It's size is the same.
Discussion
And you can see their thumbnails in the Files app? Very interesting
Yes, they have thumbnails.
https://v.nostr.build/6m6mu7Ij0fSNWMbs.mp4
This video uploaded successfully. Something strange with the encode on the others? The app I use YTDLnis did update recently as well.