Say, for example, you watch stuff PIP while browsing other content on the web, or while gaming, and you only have a single monitor.
This solution would be an elegant way to keep your content effectively minimized and squared away while still allowing you to actually watch it.
The video, no matter the resolution, would be contained in a box that matches your monitor's screen ratio. If your screen is 1280x800 like the one on the Steam Deck, or it's 1920x1080 for gaming, this could be a fun and easy way to ensure that things remain in dedicated little boxes.