These are temporary files created when you play. they are automatically deleted when you stop playing. Nothing to worry about.
Actually there is something to worry about. Temporary files should NOT be saved in the Documents folder. Period. The purpose of the "Documents" folder is to keep user saved documents, not temporary application files, not logs, not mods, not caches, not settings, not databases.
The only files it slightly makes sense to keep in the Documents folder are the game saves, the screenshots, and the recorded videos. Although the screenshots would go better in the "Pictures" folder and the videos in the, wait for it: the "Videos" folder. And the game saves are not really documents anyways, since double-clicking on one in the File Explorer doesn't automatically start the game from that save, like a regular document should. But at least those are somewhat "document-like".
The correct place to save temporary files on Windows is in the %TEMP% directory, which normally points to %LOCALAPPDATA%\Temp . This is clearly a Sims 4 bug, and the proposed solution is just a workaround for this bug.
It's clear that the developers were lazy and didn't care where files should be kept on each operating system. They just created a "bucket" for everything, and put everything there. That's fine, the software industry is not what it used to be, nobody really cares about quality anymore, so I'm not surprised by that laziness. But at least they should allow the users to choose where that "bucket" should be on their computers, not just choose for them.
