The issue is injections per power stroke.
From myturbodiesel.com:
In addition, the Passat TDI engine and HPFP is different from the Jetta-Golf-Sportwagen. VW lowered the fuel injection pressure, raised the fuel line pressure, and changed the pump/injectors which may increase reliability. The Passat HPFP has a longer stroke, its piston and bearing have a different finish, and the pump body is slightly different. VW also changed the piezo injectors on the Jetta-Golf-Sportwagen with solenoid injectors for unknown reasons. The newest (2014+) generation Golf-Audi A3 TDI engine also changed to solenoid injectors. Although the engine is rated for the same power as the Jetta-Golf engines, the turbo is slightly smaller which brings on the power slightly lower. Combined with slightly different tuning, it compensates for the heavier car.
The injection pressure on the Passat is 1800 bar...this means that if it uses a Bosch solenoid it uses the CRS2-18 which has a minimum Injection separation time of 350 microseconds. The Bosch piezo is the CRS3-20 which has a minimum injection separation time of 200 microseconds.