Though your point may be somewhat tangential to a test first or even design first discussion, I do take it.
One of the rewards of this forum for me is coming across an insight or perspective that has some novelty and fitness both.
Does an actually existing implementation provide value is exactly the question, and how quickly do we realize such value? Nimbleness and ease of reuse and ease of change are valuable, because both business needs and requirements change.
One of the points that I have seen sundial effectively make before on other threads is the consequence of business needs and the higher order problem of serving business needs effectively through the building of networks and processes and not just somewhat-trivial specific apps.
Also, to your point, the higher order problems of a google to take one example are not just the apps but the entire network and the nimbleness.