Sure they could, but then you trim the video by 2 seconds, tweak the colors, or just send it over WhatsApp, which recompresses the file with its own encoder. The hash breaks instantly. Cryptography protects bits, but video is about visual meaning. The slightest pixel modification kills the hardware signature. Plus, it does absolutely nothing to fix the "analog hole" problem - a scammer can just point that cryptographically signed iphone camera at a high-quality deepfake playing on a monitor