The underexposure in camera and process to dodge back light where he wants it -- although done in a digital environment -- relate more to the traditions of analog printing.
Underexposure is more complex because even if only a few photons have been recorded, there's a chance some detail may be recoverable -- although it's unlikely.
Factors considered may include unusual lighting distribution, variations within a camera system, filters, non-standard processing, or intended underexposure or overexposure.
Many neutral test cards are far from perfectly diffuse reflectors, and specular reflections can cause increased reflected-light meter readings that, if followed, would result in underexposure.
