What I take away from this is that when you sell yourself as a designer, you're selling your process, not your product. Even if you have a dozen great websites in your portfolio, those could all be flukes. How do you guarantee to a potential client that their site will be as good as the others? It's all about your process, and you need to stick to it. He gives examples of how they'll try to interfere, but staying true to your process is key to delivering what you promised. That said, I don't think I agree completely with his refusal to sketch before researching. Showing what you're capable of with limited resources is a common tool to gauge someone's skill, like a game jam or a writing prompt. While that client was impressed with their answer, I imagine most would like to have a little test to vet potential designers and see how they handle the task (at least if said designers aren't Big Names already).
It's interesting to think about needing to revise content for a mobile site. I admit I was in the camp that making a mobile site just meant paring down the desktop, but really they're two different things. While being the same thing. This gets confusing. The variety of devices and screens something can be viewed on isn't just a few options, it's an entire spectrum of resolutions and capabilities. You can't think in terms of "mobile site" and "desktop site," as those terms don't have definite meanings anymore. Your content must be well suited for any type of viewing, and the best way to achieve that is to start at the most limited.