Resistor in shunt regulator not following Ohm's law?
I am guessing that you are looking at an SMT resistor marked &quot;470&quot; and that it is actually 47 ohms.

As to operation-
The TL431 draws as much current as required (up to 100mA+) to reduce the voltage at the sense input to 2.495V nominally. As long as it gets &gt; 1mA to use itself it will function properly (400uA typically). If we assume the circuit draws about 10mA the base current might be of the order of 100uA.
So the 4.7K resistor needs about 5.2V across it to function (so there is 1.1mA+ flowing). Add that to the 5.6V required at the base of the transistor.
So this regulator will work from about 11.5V up to well over 21V, taking into account the drop across the 47 ohm resistor.
As @bobflux rightly points out, this is a series regulator. The NPN transistor is the pass element.