I think you're overestimating the average person. We can give people direct, scientifically-backed evidence of something, and there will still be significant groups of people fervently denying it.

The resources (money, energy, opportunity cost of engineering time) put into AI video generation are better spent elsewhere. Not pouring resources into it would hopefully stunt its progress, making AI generated propaganda lower quality and easier to spot.

Even if that were true, the little quirks of private large scale video models would be different than the public cheap ones. If anything, it would just give the public a false sense of being able to detect AI videos and overlook the more subtle flaws of privately made ones.