This argument never made any sense. The only input you have is the video or picture. If said input is made to 1:1 to what would be a real life file, then it's just an impossible solution.

Simplify this to a single pixel. You crop one pixel from a real life picture, then ask an AI to generate said pixel. Will it do it? Certainly. If on one hand, you have a pixel 150, 0, 50 (RGB values from 0 to 255), and on the other, you have a pixel 150, 0, 50, then it's physically impossible to tell which one is the real one, and which one is the generated one. No matter how good your software is, eventually it all comes down to "Just guess".

Secondly, your software to detect AI-generated content is a similar problem to the cheater / anti-cheat war that's been going in games for the past 3 decades. Guess what? Cheaters have always been winning, every single time. Every time there's an anti-cheat breakthrough and people claim "They did it! Cheaters are gone!", wait 3 months and suddenly a new wave of cheaters is here with even harder to detect methods. If you make a software that detect AI-generated content, all you do is amplify how good AI generation will be, in order to circumvent the AI-detector.