This sort of delusion bullshit just goes to show that "financial planners" and "experts" have no idea how most of the USA actually lives.
In fact, less than 60% of our country now earns enough to live a secure middle-class existence. Almost no one can afford to save any money, much less a "three to six months of living expenses." Almost everyone is in debt -- almost always due to living expenses, including medical expenses. Only 40% of the country can handle a $400 emergency.
This is America right now.
Frankly, I am impressed that Ocasio-Cortez had $7000 in the bank, and I promise you she only had that much because she had no children, and has had no medical emergencies. Before I was married and before I had cancer, I had a big chunk of money saved too.
"Plan to save 15%" is charming advice. Plan all you like. Life has other plans.