Content Strategy should be about who is my target audience and what content do I need to give them to win them (and keep them) as happy customers.
It's a good quote - no dissension here - but it makes me think that there is more to meeting customer needs than making them happy. Documentation, like usability in general, is a background function: the foreground function is that the user can use the product.
So you might produce beautiful documentation that garners raves from readers, but it doesn't actually do what it's supposed to do. For example, readers might not realize that you've omitted key information; or that they could have learned what they needed in many fewer words; or the people who find the documentation think it's brilliant, but most people can't find it. Of course there's still value in wowing readers, but that is secondary to the main purpose.
Don't get me wrong: writers need to be close to the business. They need to consciously meet business needs. But business needs might be a bit more subtle than "happy customers". And metrics that focus on the easy targets might miss the mark.