I've seen some torrents incorporating both standards in their description and I don't get it. It's either 1200p (1920x1200, WUXGA) or 1080p (1920x1080, Full HD).
Is the 1080p mode just hiding black bars present in the 1200p stream? Could be a stupid gimmick to get people to choose a particular uploader's torrents.
Yes, I've seen a video file that changes resolution mid-video, but it's more of a party trick since not all players handled it well
Specifically, I saw a group chat program rendered it "correctly" (Discord? I don't remember), so the embedded video would re-flow the rendered chatroom while playing
Not sure, but maybe "1080p" describes the approximate level of video quality ("full HD") while 1200 is the actual vertical resolution ("full HD but taller") due to the video having a non-16:9 aspect ratio?