While HPFP failures are not particularly common in our cars, if a failure occurs, it is typically a $8k -10k repair. Obviously, the Ford Powerstrokes have a similar failure mode, which might be more common. But since not all HPFPs are the same design, while the CP4 has a “bolt-on” solution to isolate the pump crankcase flow from the engine fuel supply circuit, doing the same to our VW HPFPs may not be as easy, or even possible.
As an aside, the DS4 pump in my GM 6.5 TD does not fail this way, the IP fails and is a costly replacement, but the rest of the fuel system does not get contaminated. It all depends on the design.