A factor to consider is that vast majority of people still need to work to survive. There are very few people who can live off their investments.
You (and I) may need to work. But that doesn't mean there's not a large gap between us and the "poor".
Take myself for an example - I own half my house and the bank owns the other half. So, yes, I have to work for a "survive" and pay for my mortgage and food.
But I only have to earn enough pay half the cost of housing, because the other half is provided by my capital.
A poor(er) person has to earn enough pay 100% of their cost of housing. A rich(er) person would own their house in full, so has no need to earn to pay that cost of living.
So there's clearly a scale between having to work to pay for anything, and not having to work at all because your capital pays enough dividends to cover all your bills.
The article contends that the "rich" cut off point is much lower down than we think, and that this advantage is passed from generation to generation.
The author says that in the UK this generational advantage is more recognised than in the US, because it is more formalised - which takes away some of the ability for people to be willfully ignorant of the advantage they've been given from birth compared to others.
In virtue of this monstrous system, the son of the worker, on entering life, finds no field which he may till, no machine which he may tend, no mine in which he may dig, without accepting to leave a great part of what he will produce to a master. He must sell his labour for a scant and uncertain wage. His father and his grandfather have toiled to drain this field, to build this mill, to perfect this machine. They gave to the work the full measure of their strength, and what more could they give? But their heir comes into the world poorer than the lowest savage. If he obtains leave to till the fields, it is on condition of surrendering a quarter of the produce to his master, and another quarter to the government and the middlemen. And this tax, levied upon him by the State, the capitalist, the lord of the manor, and the middleman, is always increasing; it rarely leaves him the power to improve his system of culture.
See this as an example: https://en.wikipedia.org/wiki/Madeleine_Schickedanz The article does not give much details. But managers basically stole her wealth from her and siphoned it to themselves.
"She was supported in her claim by Thomas Middelhoff". In my opinion it was Middelhoff who badly advised her for his own gain.
I wouldn't consider this rich, wealthy yes, but not rich.
Also my money is probably more in the range of the 20% of the population that is "under me" in the stats than the 2% "over me".
You still have to go to work every day like everyone else to sustain this lifestyle. You just have nicer "things" and "fancier" experiences?
Sure, it's a continuum, but "not having to live hand-to-mouth" is a hell of a lot closer to rich than to poor.