There was one guy on reddit who had a scare when his computer flashed a picture of a dead person when shutting down, and he thought his computer was haunted. It turned out to be a frame from a youtube video he was watching earlier. It may be that macOS is not that good at clearing out GPU memory sometimes.
I have the exact opposite problem. When I reboot after system updates, half a dozen YouTube videos in Chrome tabs start playing over each other on the password screen. They get through about 20 seconds before I can stop the last of them.
Audio only on the password screen, but all audible.
I’ve long had a similar problem on iOS. Whenever I return to an app, I briefly see an image from a few minutes ago. Which can be bad if I’m showing the phone to someone that old state was exposing sensitive data.