White7561, that is interesting! I'd love it if they fixed whatever this is in 12.1. That said, I'm sure that if absolutely everyone in the world using MS Teams experienced this bug, there would be a lot more Google results for it than just this thread.
I still haven't been able to make the artifact happen without Teams running though, even when playing four 4k videos in Firefox simultaneously to push CPU, GPU, and memory load to similar levels as a Teams conference call. I'm still suspicious that VS Code might be able to do it though -- maybe an Electron thing? -- and I'm going to be using that a lot today, so I'll keep paying attention.