If you're hiring PWC to do a Fit For Growth Transformation, that means you believe you need layoffs. The symptoms of are usually obvious: you're burning money, and you'll run out soon. They can be less obvious: You lose contracts based on cost, because your overhead is hire. You don't hire the PWC/FFG team if you believe you're poised for actual growth or need help hiring to move into new markets.
You can get their book. It says point-blank that FFG generally involves a 25% layoff. This isn't some big secret or inside story. It's just what they do.
The advertised value-add of PWC/FFG isn't to tell you that you need a layoff (you knew that already). The value-add is understanding how to structure that layoff. An ideal outcome of a layoff is that you've cut the corporate fat: people doing useless things with no value add. You've removed a big chunk of the corporate bureaucracy. You have faster, simpler, more agile business processes. When you want to do something, you don't need a 3-month approval from Jim in legal, Alice in finance, and Yoav in branding, since Jim, Alice, and Yoav no longer work there. On the other hand, parts of your business which contribute business value are left untouched.
Does it work? I don't know. But most executives go through this occasionally. As an executive, you're an expert on your own business. PWC/FFG has done layoffs over and over and over again. They've seen what can go right and what can go wrong. You're paying for that experience.