The idea that all/most knee pain can be cured by the correct bike "fit", regardless of the persons symptoms ,the nature of the condition, the extent of other factors/exercise/activities, and whether or not this person rides a bike for 0-100 hours a week is a dogmatic notion.

Yes it properly is his cleat set up, but other factors will play a part in the persons aliment.

If you put a person with a pre-existing knee complaint on a perfectly fitting bike it would not necessary address the initial complaint. At best it will reduce the aggravating factors involved in cycling activities enough to keep such issues in the background. "Fit" is unlikely to be a cure in itself, any more than ultra sound,resistance training ,stretching, or other modalities could be considered to be always the correct approach for every knee complaint.