I don't think anyone would suggest that there should be perfectly consistent outcomes, rather, on the whole that outcomes should be positive. We know there will

I don't think anyone would suggest that there should be perfectly consistent outcomes, rather, on the whole that outcomes should be positive. We know there will be poor performers. The study is suggesting that 'on the whole', there are negative outcomes, implying that 'most psychotherapists' are just bad at what they do, or more likely, there's a more fundamental issue with the nature of psychotherapy itself.