They play with language in a very disarming manner. Not highbrow, but will find compelling nicknames for their loved ones and deliver them in a way that is difficult not to be drawn in by.
We had a resident with Downs who needed assistance every day ...
But he got tired always asking "You help me?"... and started saying "I help you!" (and laughed)...
We knew what he meant & came over ... he got a kick out of swapping his pronouns :)
That's the thing. Something rare like Down Syndrome only has a very small selective pressure against it, and it's really easy for other effects to remove a fraction of it.
So things that seem ridiculous like this assertion or the "super uncle" theory about homosexuality are not so easily dismissed when one really thinks about them. Of course, there can be selective benefits from genes with a propensity for (forming trisomy 21, having homosexual individuals, etc) when the specific condition doesn't manifest.
And this might also be a case of one's expectations. If you spent your entire week teaching preschool, and then on the weekend met up with some adults for drinks later, you might come out of that evening with the thought that those were some of the most urbane sophisticated people you'd ever met.
Yeah... because you spend the vast majority of your day preventing toddlers from sticking crayons up their noses. It's the intellectual equivalent of the ebbinghaus illusion.