I used to be an adult special needs teacher and one of my students did this frequently. He had severe autism so I speculate that there was a sensory element to it. At lunch time, he would sit there regurgitating and re-chewing and re-swallowing his meal, over and over. He also used to just throw up whenever something didn't suit him. He was non verbal and had not learned many more socially appropriate ways of communicating so had to use a collection of somewhat "challenging" behaviours in order to tell us what he wanted.
When I first realized this had a name, I read that experts believe it occurs most in infants and adults with below-average IQs.
I suspect most adults with above/average IQs who have this hide it.