Is this screenshot from the 720p video? I used to have that file but I lost it anyway, If it is, then it's not a true HD file. If you notice down bellow there's a thin black line on the right, that's a line that shows it's from an SD interlaced video. Of course you can upscale a prores 480p or 540/576p SD file into 720p and still look crystal clear.
Edit: Also I think the other 576p video is also converted from another prores source because it should have a flag to play inside 4:3 aspect ratio even if it was 5:4 (like the dvd format) on quicktime player.