The author is very condescending,

In 2022, it is appalling that a vast number of people still think of people with Down Syndrome as children. I remember in the 70s, 80s and 90s, hearing people describing relatives with this syndrome, and ending their description with, ‘and he/she has the brain of a child.’

That is because for decades everyone we ever saw with downs behaved like a child. In the 70s they were called retarded because their brains did not develop properly. I remember a downs syndrome man in my neighborhood when I was a kid. He was at least 35, he used to copy the little kids. When they would get long trailing willow sticks from the willow tree on their way home from school and walk along trailing them behind them so you would see this 35 year old man doing the same thing so not only did he behave like a child his actions showed he also identified as a child because he wanted to do the same things they were doing.