The throttle bodies fail on these sometimes. The set a DTC, the gears strip out. Not sure what your mode of failure is, but it could indeed be bad. Not hard to replace, just three Allen screws and the electrical plug.
As for semantics: Volkswagen calls this an 'intake manifold control flap', Mercedes-Benz calls it an 'EGR throttle valve', BMW calls it a 'throttle body' (or 'throttle valve
s', where equipped), Bosch calls it a 'throttle control valve'. So whatever you choose to call it, the term 'throttle body' fits, as if you saw it laying on the bench next to one from a gas VAG product, the only way you could tell the difference is that the diesel one spring loads
open and the gas one spring loads
shut.
But for the record, ALL newer diesels do indeed have throttles, some have several, and many older diesels do as well. People should study diesel engines throughout history up to and including present day before they spout off nonsense about "diesels don't have throttles" because that simply is not true.
As far as the throttle's purpose, well that is a lessen for another day....