There are two general approaches to interface design — methodical application of scientific studies and comparisons, versus reliance on artistic talent and instinct.
Both the power and the deficiency of scientific approaches is that they require some sort of explicit model. You need to understand something about the structure of what you are looking at in order to ask sensible questions about it.
In contrast, artistic approaches to design do not necessarily require an explicit and well-understood model on the part of the designer (although there can be one). The designer does indeed always have a deep understanding of underlying structure, but the designer can be effective even if this understanding remains at the unconscious level.
We’ve all seen somebody sit at the piano, or pick up a pencil and paper, and proceed to create magic. Clearly they know a lot, and are drawing on a wealth of understanding and experience, but they don’t need to have examined that experience in order to call it forth.
Interface design might be one of those cases where the intuitive approach of a single talented artist/designer might be more effective than the methodical approach of a team of researchers.