Usually it is about behavior shifts and/or emotions. E.g. if I’d be watching videos with cute penguins and then seen a politician „adopting” penguins at zoo, that’d be a political propaganda.
Political ads have to be marked clearly but if politician is sympathetic to the platform and platform owner has a stake in keeping good relations then it’s just another penguins video, right?
And it’s omnipresent, so you stop paying attention. It’s not only China who is doing that. That’s why Paris Syndrome exists, car manufacturers don’t allow game makers to show their models in a destroyed form or why actresses don’t like to show their nostrils.
The problem with China (as far as I understand) is lack of the symmetry. They will sell you everything, but refuse to let your merchants in.
And I’d describe message shown to American users as a propaganda.
I did once see a cat that was named "Chairman Meow" in one video, which might have been very subtle CCP reprogramming now that I think on it.