Another conjecture: overroasting the beans concentrates the caffeine. Their tall (12 oz.) drip has an amazing 260 mg of caffeine. That's about double a typical cup of coffee.
That can alter personality and cause impulsive behavior, such as impulse purchases.
THAT is why they are burning their coffee.
To quote some random authors: ”evidence has shown a strong relationship between impulsivity and genetic variations of the enzyme primarily responsible for 5-HT degradation, monoamine oxidase-A (MAO-A)”
Those genetic variations change the activity of MAO-A. The same effect is acquired by habitually consuming coffee.