I'm a little bit confused of the workflow they are suggesting. I'm a web developer with "good design taste" but I definitely can't design myself, I always pair up with a designer that does the PSD. But of course this doesn't mean that when I see a navbar that has a gradient I copy a paste the image of the navbar in my website with a , my job is porting this images to HTML, CSS and JS. If you're actually putting image…
This has the obvious advantage that when you're "done" with your design, the UI code is already written.
Of course it's way easier to do things like adjust gradients in photoshop. I also assume that most people will be able to do things in photoshop that they might not know how to do in HTML/CSS.