Ignoring the ... quality issues of this post, looking at the statistics of wealth _is_ interesting.
The author points out a couple times the sub-optimal investment strategies apparent in this data, and reads into them under the assumption that the wealthy must have some trick of their sleeves and so their investment strategies must just go _beyond_ us mere mortals.
I don't concur. I think, rather, most everyone is financially naive. _Especially_ wealthy people. Why? Here's an example.
Doctors make a lot of money. And yet the vast majority of doctors are abysmal when it comes to A) running a business and B) managing money. And it makes sense, because doctors have to spend the vast majority of their young adult lives in school, and then the rest of their lives in a high stress, high demand work place. There's no time to pick up those skills.
There's no reason to suspect that anything different happens for the wealthy in America. You don't just acquire skill with money simply because you have or it, or earn a lot of it. Most of the super wealthy are people like actors, athletes, etc. None of them would have the time or inclination to be proficient in finance.
Even in the case of wealthy business people, aptitude in business does not necessarily translate into aptitude with money. It sounds a bit contradictory at first glance, but managing finances is actually one of the least important things when it comes to running a business. It's mostly an after thought. It's just that it tends to be salient and a common topic of discussion. Zuckerberg isn't wealthy because he's good with money. He's wealthy because he had a good business idea with good execution. It's why the CEO isn't a CFO.
In other words, at the very least I believe the wealthy are as illiterate when it comes to money as the average American. But more likely they're worse, because being successful tends to mean being hyper focused on one specific goal in exclusion of other things.
And don't forget, your ideas about what wealth looks like and how the wealthy live ... comes mostly from celebrities; people who build their business on appearances. So no wonder they want to portray an image of 1) extravagance and 2) aptitude.