Why would a physical knob (as present on the Surface Studio), which serves the function of a physical knob, be deemed skeuomorphic?
Is it an actual physical interface? I must be thinking of a different product.
Yes, it's even in the thumbnail for the video. (Hint: To the left of the keyboard.)
It's basically a rotary encoder attached to a chunk of aluminum with a capacitive elephant on the bottom, so the screen can sense where it's being placed.
Griffin actually makes a similar, standalone (non-touch screen) product that works with any Mac or PC. They come in wired and wireless versions. Basically a machined block of aluminum with a clear rubberized base (which houses LEDs for user feedback). They have a full API available for third party developers to integrate it into their software. It's pretty neat, actually. (I bought one back in 2003 or so when they originally came out with them. Was nice for scrubbing video and scrolling long documents.)