This seems like a way that device attestation could worm its way further into our devices. Right now Google is trying to watermark AI-generated photos as AI, but you could easily go the other way - if a photo hasn't been manipulated, it's signed with a key that is locked down to device attestation. What, your phone is rooted? That's kinda suspicious - how am I supposed to know your photos are real?
Short of that, though, I suspect that the most likely consequence of this is the videos will start being increasingly seen as necessary for true proof, since those are harder to fake - for now, at least. And of course, there will be a lot more misinformation on the internet, especially in the short term while awareness of this catches up.