I'm a freelancer so I don't know. personally i prefer the en.wikipedia.org/wiki/Design-driven_development with dummy data.
and her approach https://www.youtube.com/watch?v=7OSkB4BCx00 seams to be pretty solid to me :)
As a developer I know that we need to stay "agile", but getting a mockup first than iterating over different parts with the designers and after taking out the "scope breaking" features showing the customer feedback speeds up your process and reduces overhead :)