It's likely that Behrens only performs the cocci experiment to humor Hans—in truth, this strain of bacteria exists in all humans, so it’s really not indicative of any serious, underlying problem that the cocci develop in the petri dishes. Yet Behrens, apparently sensing that Hans wants some reason to justify his indefinite stay at the Berghof, goes along with the test and orders Hans to remain at the sanatorium. Hans’s willingness to go along with this phony prescription despite his new awareness that his inner malaise (“the demon”) is slowly destroying him signals his continued resistance to learn from his mistakes. He knows that staying at the Berghof is slowly destroying him, yet he can’t translate that knowledge into practical action.