Plenty of consultancies publish logos and percentage improvements. We deliberately do not.
Several of our engagements involve public-sector operations, personal data or commercially sensitive processes. Naming those clients, or publishing figures precise enough to identify them, would be a poor way to demonstrate that we take confidentiality seriously.
It also keeps us honest. A performance number from one organization's process, with its own data quality and staffing, tells you very little about what would happen in yours. We would rather describe the problem accurately and then talk about your numbers.
In a conversation under a mutual NDA we can go considerably deeper — architecture, decisions, what went wrong and what we would do differently.