Yet the metaphor works. Everyone knows what business casual means, which is a key to quick understanding. A business casual voice is serious but light, focused on ease, deliberately avoiding the stuffy. Business casual is more interested in what it is doing for the audience than the writer or performer. Business casual is about communication, not obfuscation.
I have worked with a lot of content originators and subject matter experts who write the same way they learned in high school; stiff, formal, you know — boring. For a doc such as a technical white paper boring = death. Even worse, boring means nobody reads it.
I’m going to use the business casual metaphor next time I need to make this point. Somewhere in between a suit and cargo shorts, editorially speaking, are the comfortable khakis that will deliver you message in a serious but approachable manner.