The way ATOS works seems to deliberately rule against understanding mental health problems. The man in the programme I mentioned could get himself dressed and could get up from the table and hold a pen, questions that were used by ATOS according to his sister, but that didn't mean he was able to go out, get a job, and work!
Similarly, I know someone who is paraplegic, he was disabled in a rugby accident aged 15. He can just about use a computer with disability enabled hardware and he does do some work from home. However, ATOS stopped his benefits and in his assessment he was told things like 15 minutes was too long for doing a poo! He is bright, poor chap, and he appealed and was successful but not everyone can do that and they have to wait long periods before the appeal is heard.