In all seriousness, just to say "a well-fitting bike doesn't have any headset spacers" is ridiculous because you can achieve the exact same fit with a horizontal stem and spacers, or with an up-angled stem and no spacers. If their contention is that the right frame size would lead to a correct fit with a more-or-less horizontal stem and no spacers, well maybe but you're still at the mercy of what the frame makers are putting out.