A stated willingness to turn work away is cheap to write and common on sites like this one. What makes it real is having the specific cases written down in advance, so that the decision is not being made by whoever reads the enquiry on a slow month.
The clearest case is a problem that is not a commercial-system problem. If what is failing is delivery, or hiring, or a product that does not do what it claims, a diagnosis of positioning, offer, journey and sales will measure the wrong thing and report accurately on something that is not the issue.
The other cases
A business looking for volume rather than reformation. The work here retires practices, which costs something in the short term, and a buyer who wants more of the current motion will experience that as obstruction and will be right to resent it.
A business where the person commissioning the work cannot authorise the changes it would recommend. A reformation touches pricing, positioning and how people sell, and an engagement bought by someone who can only influence those is an expensive way to produce a document.
A business in genuine financial distress. The horizon on this work is measured in quarters. A firm that needs revenue this month needs something else, and taking the engagement would be taking money for a timeline that cannot help.
Why it is written on the site
Publishing the exclusions costs some enquiries and improves the rest. A buyer who reads them and proceeds has already excluded themselves from the categories where this would go badly, which makes the first conversation about their situation rather than about qualification.