That is a good point. My understanding is that there are different types of producers, and some lean more technical, while others lean more consultative, and Rubin is falls in the latter camp. Contrast that to other more technical producers like Phil Spector, or Dave Fridmann whos productions have a very distinctive sound.

My observation is that it seems like his skill is helping the artist see their work in a different way, helping them make creative decisions, and just generally offering counsel around how to make the best possible work. This process doesn't manifest in a specific sound, and each production is different based on the needs of the artist.