Rather than seeing it as an actual claim about adults, see it is a representation of someone's mental model that there will always be people who are like adults are to a child.
In fact, when you get a job, you are now an adult in the room, so you better act like it. It's one of the many ideas that when you bring it up to the conscious level it's drop-dead obvious, but the idea that there will be other responsible people can lurk in the lower parts of your mind for a long time, and it can take a lot of time to clear the idea out. Thinking about it consciously is unfortunately not a full solution to that problem, but it certainly can be a huge help.
It's the same sort of thing as imposter syndrome; it's not that you're literally an imposter, in fact many sufferers of imposter syndrome may well be above average, it's a statement about internal perceptions.
When I first entered the workforce I remember someone pulling me to the side and used this exact metaphore. Told me there were adults and children and I needed to start treating certain people as adults rather than equals (more or less, I'm paraphrasing, but this was the meaning).
I was blown away that anyone actually had that attitude toward others. I was probably 21 I think?
I mean, I get it on one level with respect to politics, but screw that.
In fact, when you get a job, you are now an adult in the room, so you better act like it. It's one of the many ideas that when you bring it up to the conscious level it's drop-dead obvious, but the idea that there will be other responsible people can lurk in the lower parts of your mind for a long time, and it can take a lot of time to clear the idea out. Thinking about it consciously is unfortunately not a full solution to that problem, but it certainly can be a huge help.
It's the same sort of thing as imposter syndrome; it's not that you're literally an imposter, in fact many sufferers of imposter syndrome may well be above average, it's a statement about internal perceptions.