turbulentDFSEMInlet; Removal of 'mapMethod' causes FOAM FATAL IO ERROR

Summary

When mapMethod option of turbulentDFSEMInlet BC is removed, it raises FOAM FATAL IO ERROR although under turbulentDFSEMInletFvPatchVectorField.H was stated for its usage was stated to be optional:

     Property  | Description         | Required         | Default value
     mapMethod | Method to map reference values | no | planarInterpolation

--> FOAM FATAL IO ERROR: 
'mapMethod' not found in dictionary "/home/snoopy2/kuta/OpenFOAM/kuta-v1806/run/channel395DFSEM/0/U.boundaryField.inlet"

file: /home/snoopy2/kuta/OpenFOAM/kuta-v1806/run/channel395DFSEM/0/U.boundaryField.inlet

    From function const Foam::entry& Foam::dictionary::lookupEntry(const Foam::word&, bool, bool) const
    in file db/dictionary/dictionary.C at line 332.

FOAM exiting

Steps to reproduce

Please consider tutorials/incompressible/pimpleFoam/LES/channel395DFSEM case.

Remove mapMethod under 0/U:

    inlet
    {   
        type            turbulentDFSEMInlet;
        ...
        mapMethod       nearestCell;
        ...
    }   

to

    inlet
    {   
        type            turbulentDFSEMInlet;
        ...
    }   

Then execute the following respectively:

blockMesh

decomposePar

What is the expected correct behavior?

Either the documentation in turbulentDFSEMInletFvPatchVectorField.H should be corrected, or the method according to the documentation.