Yes, you're correct about private keys getting exposed, but it's better than nothing. I suspect though, even after key exposure there may be a way to make new private keys so that compromised keys have a known point when they are compromised, which makes public how much skepticism we should all have about authenticity.

I just think there is a world of difference between "certainty" and "plausibility" when it comes to videos on the internet. Yes, state actors might circumvent it, and skepticism should remain, but there is a world of difference between North Korea trying to convince me of some political scandal, and Pepsi Co trying to convince me that someone I trust loves Pepsi.