It is technically true that the people involved are unable to adequately formalize their actual requirements, but that is because precisely formalizing their requirements is a problem much harder than human mathematicians or computer scientists have ever solved. All humans would be "unwilling or unable to adequately formalize their actual requirements." Notice, for example, that mathematicians can't precisely formalize modern mathematics in the required sense either, and that problem is still much easier than formal verification for the sorts of things modern commercial projects are trying to accomplish.