I’m not the person you responded to, but I’ve lived with a person who had a case of OCD that I’m confident saying is definitely not adaptive. To give one anecdote among many, this person would spend the entire day in the shower because they got a spot of grease on their pants. Episodes of this severity were common (ie. sometimes happening daily for extended stretches of time). They explained the cause of the behavior as a failure of communication between the part of the brain and solves a problem and the part that needs to acknowledge that the problem has been solved so the solving can stop. I don’t know if that tracks with psychiatry, but explanation made sense to me.