I’m not sure it is about designers understanding business as much as it is about them understanding what they are trying to do. Design isn’t just visuals, it’s broader problem solving. You can give a beautiful answer without understanding the problem, but only give a great answer when you fully understand the problem.
Being good at strategy or design or writing is more than overt craft. It’s knowing why and how and when to apply that craft. Having intention. It’s not just the way something looks, it’s how it works.
Coincidentally, this is why Brandcenter graduates kick so much ass when they get out of school. They are good at problem solving and making killer work that actually works. It’s a transformation.
…though I might be a little biased.