Dedicated circuit for **Sub Zero** refrigerator - any code requirement?
NEC 110.3(B)  Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.


This is because the labeling and instructions are part of the UL listing. UL only tests and certifies the appliance if used according to labeling.  So UL has not tested what happens if the refrigerator shares a circuit, and their certification is void if it is used on a shared circuit.

Why they'd want that

Possibly the motor is high-draw when it runs, such that it consumes nearly 80% of a 15A circuit's output, particularly when initially chilling the refrigerator down from warm.    They definitely don't want their fridge on a GFCI; that produces special challenges for a fridge, especially one with a large motor that is built by a small volme producer. Though they can't give that as the primary reason, of course. .

Obviously the manufacturer would not place that requirement lightly, because it prevents them from selling fridges to people without dedicated fridge circuits.  They are pretty high-end, so maybe they expect their customers to ante up.  (Compare: appliance makers have fought tooth and nail to keep the old NEMA 10 groundless stove/dryer connections from being outlawed). 

I also suspect UL would push back on them and discourage them from imposing that requirement if it wasn't necessary.