That sort of goes with the psychological theory of "projected image." When a psychologist sees a person's projected image, he thinks the person is overcompensating to hide a defect . . . Examples: a person who acts very tough because inside they feel weak and vulnerable . . . A person who tries to make themselves beautiful because inside they feel ugly . . . A person who drives a loud or flashy vehicle to be noticed because inside they feel invisible . . . A person who brags because inside they feel empty and worthless.

I think that perhaps some people act "super mature" to compensate for feelings of being childish. And I guess it would follow that since this "super mature" image is a facade that their childishness would escape from time to time.

Don't know if this theory is correct. It is just one of many psychological theories out there to explain behavior. I suspect we all have things that get on our nerves and things about ourselves that get on other people's nerves. I know I do. It can be aggravating.