We have that too. A second computer works wonders here. Worse is the training I'm doing now which lets you run it in the background but makes you push a button every 30s to continue the training.
Next step, ever watched "15 million merits", an episode of Black Mirror? If you close your eyes, an excruciating sound requires you to open them again and continue watching.
There is something to be said for employers that are less technologically organized and competent. A friend at a company that did this used a virtual machine to run the training.
Ten years later, you will nostalgically think about the good old trainings in 2020 when the web camera yet didn't watch your eyeballs and analyze your face expressions in order to determine whether you need to watch the training again.
There's no good way to certify people on this knowledge from the organization's perspective. Just get your phone out if you're feeling confident in it.
You don't even need to do that. I found a demo for the page visibility api[1] (presumably what they use to detect whether the tab is focused), and found that having the window not minimized is sufficient to make the tab think it's focused. That is, all you have to do is move the tab to a new window, and click your main window. Now your training video is in the background and not taking up any screen space (you can mute the tab if you want), but the page doesn't realized it's not focused/visible.