Interesting video but I think the problem lies, as with metagaming and powergaming, in definition. I wouldn't necessarily use the phrase "social contract" when referring to prepping a game, or setting up the scenario and getting players involved. For me social contract is pretty much gaming etiquette. But obviously your definition is much broader than that.
The problem lies in then calling people wrong when in truth all it is is that they, by their own definition of social contract, don't consider what they do as within the scope of that definition whilst it is for other people. I think this could lead to unnecessary disagreements.
So I don't think someone is by default wrong because their definition of social contract differs from yours. My definition differs from yours. I do a lot of the things that you mention but I don't consider that social contract, just prepping and setting the rules. As stated above, for me a social contract is about good gaming etiquette.
Do I have a social contract? Yes, by my definition. In as much as I define clearly what is and what is not acceptable in terms of player behaviour. By your definition I also engage in social contracts but much of what you term social contract I don't agree is. So if I didn't lay down the law regarding manners at the table then I would say I did not engage in a social contract.
Regardless of definition, I think it is true that we do a lot of these things quite instinctively and one aspect of the term is that it seems to imply something structured and signed for, rather than just good prep work and manners.