MRF - non zero flux through walls in nonRotatingPatches

Summary

When including a patch in nonRotatingPatches, even if the patch is a wall, the flux through the patch is not 0. Indeed, printing phi from adjustPhi.C results in both an inflow and an outflow - which are equals and therefore cancel out, but in my opinion, should not be there. In a real-life problem, this might result in a conservation error in the case of a closed domain due to a small discrepancy between inflow and outflow.

Steps to reproduce

print out flux through patches (e.g. replace lines 61 onwards of adjustPhi.C with

            	scalar massInStart = massIn;
            	scalar massOutStart = fixedMassOut;
                forAll(phip, i)
                {
                    if (phip[i] < 0.0)
                    {
                        massIn -= phip[i];
                    }
                    else
                    {
                        fixedMassOut += phip[i];
                    }
                }
                Info << "Mass in  " << phip.patch().name() << endl;
                Info << "equal to " << massIn- massInStart << endl;

                Info << "Mass out " << phip.patch().name() << endl;
                Info << "equal to " << fixedMassOut - massOutStart << endl;

and simpleFoam on the attached tutorial (modified from mixerVessel2DAMI)

mixer2D.tar.gz

What is the expected correct behavior?

I would expect phi equal to 0 both inflow and outflow

Environment information

OpenFOAM v2112

Possible fixes

I tried to fix the issue by forcing flux to 0 in MRFZoneTemplates.C on the excludedFaces, but I don't believe this is correct.