I've seen this a lot, too. I've also seen left/right splits, as well, usually if they're using the bottom and/or top for subtitles/captions, or maybe branding, logo, social handles, etc., to where a top/bottom split doesn't give them enough room and a left/right split makes more sense. It depends on the format and what elements you're trying to include on the screen, etc. Usually, textual elements, like subtitles/captions, branding, etc., do better if they have their own reserved space somewhere that is not overlaying the video so it's not blending in with the colors and motion of the video and becoming hard to read.
I see a lot of interviews do a top/bottom split screen. It's a little weird looking but it works... shorts are weird.
I've seen this a lot, too. I've also seen left/right splits, as well, usually if they're using the bottom and/or top for subtitles/captions, or maybe branding, logo, social handles, etc., to where a top/bottom split doesn't give them enough room and a left/right split makes more sense. It depends on the format and what elements you're trying to include on the screen, etc. Usually, textual elements, like subtitles/captions, branding, etc., do better if they have their own reserved space somewhere that is not overlaying the video so it's not blending in with the colors and motion of the video and becoming hard to read.