Pretty close - but "souping" is when you add some random ingredient that destroys the negatives but creates an interesting effect when developing the photos. You can use vinegar, lemon juice, vodka, bleach, any number of chemicals that create different effects;
In the context of the article, it seems the consultants would take copious notes (the negatives) and then go back and 'soup' them in order to have something interesting to present even though it's an unrealistic picture of the office.
