Elbows have always been allowed on the table. The rule for fancy dining was that you couldn't have elbows on the table during a course, i.e., when people are actively eating, but before/after, it's fine. That's a reasonable rule to be considerate of space.
If you have a large number of people eating in comparison to the size of the table, and the table is already covered in food, the only place on the table to put your elbows is in other people's personal space.
The rule should be "no elbows right next to someone else's food" but neurotypicals are terrible at communicating due to their underdeveloped social skills and empathy.
People other than you, who are not "neurotypicals" whatever tf that even means, are able to accomplish seating large amounts of people at a table and use basic table manners just fine. It's just common courtesy.
Yes, neurotypicals are indeed able to have large family dinners. But they have to do it using table manners as a crutch. They can't just have an honest conversation about what's really necessary, they need to rely on this social construct to tell people what to do without explaining why. It's a great weakness. If only the average person weren't so afraid to introspect and to question why we do things.
Which is kind of the point he is making. Instead of engaging in a honest talk and understanding the reasoning behind social norms, they are just pushed as normative and understandably confusing to people who struggle with "just behave like everyone else, lol".
Ironically this is exposing us neurotypicals to be socialy underdeveloped instead of non neurotypical people.
As someone who can't sit straight I only wore shorts and trousers until I learnt this trick in my twenties. While I personally don't find it lewd, other people clearly do and I get so pissed off every time someone feels the need to inform me that they've been looking up my skirt.