I am trying to understand this fuel system on the SRT6 / AMG cars.

The fuel pressure regulator is integrated into the fuel filter. I understand that. I even understand the "returnless fuel rail" and that it reduces evaporative emissions by not returning heated fuel to the tank. I don't like it, but; ok.

I do not understand why the fuel filter/regulator has a hose going from what appears to be the regulator diaphragm to the charcoal canister. It is not a boost/vacuum referenced fuel pressure regulator, right? Does anyone have data logs of fuel pressure? Is it constant relative to atmospheric pressure? The fuel pressure seems to be constant, regardless of boost or vacuum in the intake manifold. So why the hose connection? Does the ECU selectively use vacuum/boost to adjust the fuel pressure for emissions?