A new agency has no testimonial wall, and faking one is both common and obvious. The alternative is proof a sceptical buyer can verify without our help: a phone number that answers, a public commit history, published pricing, and comparison pages that concede where competitors win.
Buyers in this category have been burned, and they have learned to discount testimonials to roughly zero. Something checkable in two minutes outperforms fifteen quotes they cannot verify. The demo does more work than any case study we could write, because it fails in front of them if it is going to.
Scale. This approach does not work for a company with thirty salespeople, and it caps growth at the rate one engineer can deliver. It is the right trade at this size and it would be the wrong one at ten times the size, which is worth saying rather than dressing it up as a permanent philosophy.